[ATfL] Make sure the bootstrap compiler is being built with -O2, not -O3

According to CMake default settings:

CMAKE_ASM_FLAGS_RELWITHDEBINFO:STRING=-O2 -g -DNDEBUG
CMAKE_CXX_FLAGS_RELWITHDEBINFO:STRING=-O2 -g -DNDEBUG
CMAKE_C_FLAGS_RELWITHDEBINFO:STRING=-O2 -g -DNDEBUG

CMAKE_ASM_FLAGS_RELEASE:STRING=-O3 -DNDEBUG
CMAKE_CXX_FLAGS_RELEASE:STRING=-O3 -DNDEBUG
CMAKE_C_FLAGS_RELEASE:STRING=-O3 -DNDEBUG

As we want the bootstrap compiler to be stablest possible,
we'd rather build it at O2 than O3 optimization level.

Author: pawosm-arm

arm-software/linux/build.sh

@@ -269,7 +269,7 @@ bootstrap_compiler_build() {
 
     run_command cmake ${CMAKE_ARGS} -G Ninja "${SOURCES_DIR}/llvm" \
         -DBUILD_SHARED_LIBS=False \
-        -DCMAKE_BUILD_TYPE=Release \
+        -DCMAKE_BUILD_TYPE=RelWithDebInfo \
         -DCMAKE_SKIP_RPATH=No \
         -DCMAKE_SKIP_INSTALL_RPATH=No \
         -DCMAKE_INSTALL_PREFIX="${BUILD_DIR}/bootstrap_compiler" \