add BUILD_WITH_CLANG flag

Author: joeyjiaojg

build.sh

@@ -221,11 +221,12 @@ BUILD_DIR="./${BUILD_TYPE}-build"
 
 rm -rf "${BUILD_DIR}"
 mkdir "${BUILD_DIR}"
+EXTRA_FLAGS=""
+[ "${BUILD_WITH_CLANG}" != "" ] && EXTRA_FLAGS="-DCMAKE_CXX_COMPILER=$LLVM_DIR/bin/clang++ -DLLVM_DIR=$LLVM_DIR"
 cmake -D CMAKE_BUILD_TYPE:STRING="${BUILD_TYPE}" \
     -DSVF_ENABLE_ASSERTIONS:BOOL=true            \
     -DSVF_SANITIZE="${SVF_SANITIZER}"            \
-    -S "${SVFHOME}" -B "${BUILD_DIR}" \
-    -DCMAKE_CXX_COMPILER=$LLVM_DIR/bin/clang++ -DLLVM_DIR=$LLVM_DIR
+    -S "${SVFHOME}" -B "${BUILD_DIR}" ${EXTRA_FLAGS}
 cmake --build "${BUILD_DIR}" -j ${jobs}
 
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