Improve Occlum GCC toolchain with new wrappers for binaries

This commit makes the toolchain easier to use in two folds:
1. When compiling C/C++ source files, no need to add "-fPIC -pie" flags manually;
2. When running executables generated by the Occlum toolchain on Linux, no
need to set the `LD_LIBRARY_PATH` manually.

demos/hello_bazel/README.md

@@ -10,7 +10,7 @@ When completed, the resulting `hello-world` can be found in `examples/cpp-tutori
 
 2. (Optional) Run `hello-world` on Linux
 ```
-LD_LIBRARY_PATH=/usr/local/occlum/x86_64-linux-musl/lib ./examples/cpp-tutorial/stage3/bazel-bin/main/hello-world
+./examples/cpp-tutorial/stage3/bazel-bin/main/hello-world
 ```
 
 3. Run `hello-world` on Occlum

demos/hello_bazel/build_bazel_sample.sh

@@ -7,4 +7,4 @@ git clone https://github.com/bazelbuild/examples/ .
 cd cpp-tutorial/stage3
 export CC=/opt/occlum/toolchains/gcc/bin/occlum-gcc
 export CXX=/opt/occlum/toolchains/gcc/bin/occlum-g++
-bazel build --cxxopt=-std=c++11 --copt=-fPIC --linkopt=-pie //main:hello-world
+bazel build --cxxopt=-std=c++11 //main:hello-world

demos/hello_c/Makefile

@@ -1,12 +1,11 @@
 CC := occlum-gcc
-CFLAGS := -fPIC -pie
 
 .PHONY: all clean
 
 all: hello_world
 
 hello_world: hello_world.c
-	$(CC) $(CFLAGS) $^ -o $@
+	$(CC) $^ -o $@
 
 clean:
 	rm -rf hello_world

demos/hello_c/README.md

@@ -9,7 +9,7 @@ make
 Or you can build `hello_world` with CMake
 ```
 mkdir build && cd build
-cmake ../ -DCMAKE_C_COMPILER=occlum-gcc -DCMAKE_C_FLAGS="-fPIC -pie"
+cmake ../ -DCMAKE_C_COMPILER=occlum-gcc
 make
 cd ..
 cp build/hello_world .

demos/hello_cc/Makefile

@@ -1,5 +1,5 @@
 CXX := occlum-g++
-CXXFLAGS := -std=c++11 -fPIC -pie
+CXXFLAGS := -std=c++11
 
 .PHONY: all clean
 

demos/hello_cc/README.md

@@ -9,7 +9,7 @@ make
 Or you can build `hello_world` with CMake
 ```
 mkdir build && cd build
-cmake ../ -DCMAKE_CXX_COMPILER=occlum-g++ -DCMAKE_CXX_FLAGS="-fPIC -pie"
+cmake ../ -DCMAKE_CXX_COMPILER=occlum-g++
 make
 cd ..
 cp build/hello_world .
@@ -18,7 +18,7 @@ Either way, the resulting `hello_world` can be found in the current directory.
 
 2. (Optional) Run `hello_world` on Linux
 ```
-LD_LIBRARY_PATH=/usr/local/occlum/x86_64-linux-musl/lib ./hello_world
+./hello_world
 ```
 
 3. Run `hello_world` on Occlum

demos/https_server/download_and_build_mongoose.sh

@@ -10,8 +10,7 @@ CC=occlum-gcc ./config \
   --prefix=/usr/local/occlum/x86_64-linux-musl \
   --openssldir=/usr/local/occlum/ssl \
   --with-rand-seed=rdcpu \
-  no-zlib no-async no-tests \
-  -fPIC -pie
+  no-zlib no-async no-tests
 make -j
 sudo make install
 popd
@@ -25,5 +24,5 @@ popd
 
 # 3. Build the https server example in mongoose
 pushd mongoose_src/examples/simplest_web_server_ssl
-CC=occlum-gcc CFLAGS_EXTRA="-Wno-format-truncation -fPIC -pie" make
+CC=occlum-gcc CFLAGS_EXTRA="-Wno-format-truncation" make
 popd

demos/https_server/run_https_server_in_linux.sh

@@ -1,5 +1,4 @@
 #!/bin/bash
-export LD_LIBRARY_PATH=/usr/local/occlum/x86_64-linux-musl/lib:$LD_LIBRARY_PATH
 https_server=simplest_web_server_ssl
 set -e
 

demos/tensorflow_lite/patch/fix-tflite-Makefile-v1.15.0-rc0.diff

@@ -1,27 +1,8 @@
 diff --git a/tensorflow/lite/tools/make/Makefile b/tensorflow/lite/tools/make/Makefile
-index 73c50d3..3cef7fa 100644
+index 73c50d3..4a6445a 100644
 --- a/tensorflow/lite/tools/make/Makefile
 +++ b/tensorflow/lite/tools/make/Makefile
-@@ -42,7 +42,7 @@ INCLUDES := \
- -I$(OBJDIR)
- # This is at the end so any globally-installed frameworks like protobuf don't
- # override local versions in the source tree.
--INCLUDES += -I/usr/local/include
-+INCLUDES += -I/usr/local/occlum/x86_64-linux-musl/include
- 
- # These are the default libraries needed, but they can be added to or
- # overridden by the platform-specific settings in target makefiles.
-@@ -59,7 +59,8 @@ CXXFLAGS := -O3 -DNDEBUG -fPIC
- CXXFLAGS += $(EXTRA_CXXFLAGS)
- CFLAGS := ${CXXFLAGS}
- CXXFLAGS += --std=c++11
--LDOPTS := -L/usr/local/lib
-+LDOPTS := -L/usr/local/occlum/x86_64-linux-musl/lib
-+LDFLAGS := -pie $(LDOPTS)
- ARFLAGS := -r
- TARGET_TOOLCHAIN_PREFIX :=
- CC_PREFIX :=
-@@ -80,6 +81,12 @@ BENCHMARK_BINARY_NAME := benchmark_model
+@@ -80,6 +80,12 @@ BENCHMARK_BINARY_NAME := benchmark_model
  MINIMAL_SRCS := \
  	tensorflow/lite/examples/minimal/minimal.cc
  
@@ -34,7 +15,7 @@ index 73c50d3..3cef7fa 100644
  # What sources we want to compile, must be kept in sync with the main Bazel
  # build files.
  
-@@ -133,7 +140,8 @@ $(wildcard tensorflow/lite/*/*/*test.cc) \
+@@ -133,7 +139,8 @@ $(wildcard tensorflow/lite/*/*/*test.cc) \
  $(wildcard tensorflow/lite/*/*/*/*test.cc) \
  $(wildcard tensorflow/lite/kernels/*test_main.cc) \
  $(wildcard tensorflow/lite/kernels/*test_util.cc) \
@@ -44,7 +25,7 @@ index 73c50d3..3cef7fa 100644
  
  BUILD_WITH_MMAP ?= true
  ifeq ($(BUILD_TYPE),micro)
-@@ -209,6 +217,7 @@ include $(wildcard $(MAKEFILE_DIR)/targets/*_makefile.inc)
+@@ -209,6 +216,7 @@ include $(wildcard $(MAKEFILE_DIR)/targets/*_makefile.inc)
  
  ALL_SRCS := \
  	$(MINIMAL_SRCS) \
@@ -52,7 +33,7 @@ index 73c50d3..3cef7fa 100644
  	$(PROFILER_SRCS) \
  	$(PROFILER_SUMMARIZER_SRCS) \
  	$(TF_LITE_CC_SRCS) \
-@@ -225,14 +234,18 @@ LIB_PATH := $(LIBDIR)$(LIB_NAME)
+@@ -225,14 +233,18 @@ LIB_PATH := $(LIBDIR)$(LIB_NAME)
  BENCHMARK_LIB := $(LIBDIR)$(BENCHMARK_LIB_NAME)
  BENCHMARK_BINARY := $(BINDIR)$(BENCHMARK_BINARY_NAME)
  MINIMAL_BINARY := $(BINDIR)minimal
@@ -73,7 +54,7 @@ index 73c50d3..3cef7fa 100644
  LIB_OBJS := $(addprefix $(OBJDIR), \
  $(patsubst %.cc,%.o,$(patsubst %.c,%.o,$(patsubst %.cpp,%.o,$(TF_LITE_CC_SRCS)))))
  
-@@ -252,7 +265,7 @@ $(OBJDIR)%.o: %.cpp
+@@ -252,7 +264,7 @@ $(OBJDIR)%.o: %.cpp
  	$(CXX) $(CXXFLAGS) $(INCLUDES) -c $< -o $@
  
  # The target that's compiled if there's no command-line arguments.
@@ -82,7 +63,7 @@ index 73c50d3..3cef7fa 100644
  
  # The target that's compiled for micro-controllers
  micro: $(LIB_PATH)
-@@ -276,6 +289,14 @@ $(MINIMAL_BINARY): $(MINIMAL_OBJS) $(LIB_PATH)
+@@ -276,6 +288,14 @@ $(MINIMAL_BINARY): $(MINIMAL_OBJS) $(LIB_PATH)
  
  minimal: $(MINIMAL_BINARY)
  

demos/tensorflow_lite/run_tflite_in_linux.sh

@@ -1,5 +1,4 @@
 #!/bin/bash
-export LD_LIBRARY_PATH=/usr/local/occlum/x86_64-linux-musl/lib:$LD_LIBRARY_PATH
 set -e
 
 show_usage() {

tools/toolchains/gcc/build.sh

@@ -47,9 +47,26 @@ make install
 # Remove all source code and build files
 rm -rf ${BUILD_DIR}
 
-# Link the toolchain directory
-ln -sf ${INSTALL_DIR}/bin/${TARGET}-gcc ${INSTALL_DIR}/bin/occlum-gcc
-ln -sf ${INSTALL_DIR}/bin/${TARGET}-g++ ${INSTALL_DIR}/bin/occlum-g++
-ln -sf ${INSTALL_DIR}/bin/${TARGET}-ld ${INSTALL_DIR}/bin/occlum-ld
-ln -sf ${INSTALL_DIR}/x86_64-linux-musl/lib/libc.so /lib/ld-musl-x86_64.so.1
+# Generate the wrappers for executables
+cat > ${INSTALL_DIR}/bin/occlum-gcc <<EOF
+#!/bin/bash
+${INSTALL_DIR}/bin/${TARGET}-gcc -fPIC -pie -Wl,-rpath,${INSTALL_DIR}/${TARGET}/lib "\$@"
+EOF
+
+cat > ${INSTALL_DIR}/bin/occlum-g++ <<EOF
+#!/bin/bash
+${INSTALL_DIR}/bin/${TARGET}-g++ -fPIC -pie -Wl,-rpath,${INSTALL_DIR}/${TARGET}/lib "\$@"
+EOF
+
+cat > ${INSTALL_DIR}/bin/occlum-ld <<EOF
+#!/bin/bash
+${INSTALL_DIR}/bin/${TARGET}-ld -pie -rpath ${INSTALL_DIR}/${TARGET}/lib "\$@"
+EOF
+
+chmod +x ${INSTALL_DIR}/bin/occlum-gcc
+chmod +x ${INSTALL_DIR}/bin/occlum-g++
+chmod +x ${INSTALL_DIR}/bin/occlum-ld
+
+# Make symbolic links
+ln -sf ${INSTALL_DIR}/${TARGET}/lib/libc.so /lib/ld-musl-x86_64.so.1
 ln -sf ${INSTALL_DIR} /usr/local/occlum