Fix build

.github/actions/build-manylinux/entrypoint.sh

@@ -18,11 +18,13 @@ fi
 
 # build
 mkdir build
+export CC="$(pwd)/llvm/bin/clang"
+export CXX="$(pwd)/llvm/bin/clang++"
 export LLVM_DIR=$(llvm/bin/llvm-config --cmakedir)
 export LIBUNWIND_PREFIX="$(pwd)/llvm"
 (cd build && cmake .. -DCMAKE_BUILD_TYPE=Release \
-                      -DCMAKE_C_COMPILER="$(pwd)/llvm/bin/clang" \
-                      -DCMAKE_CXX_COMPILER="$(pwd)/llvm/bin/clang++" \
+                      -DCMAKE_C_COMPILER=${CC} \
+                      -DCMAKE_CXX_COMPILER=${CXX} \
                       -DLIBUNWIND_PREFIX="${LIBUNWIND_PREFIX}")
 cmake --build build --config Release -- VERBOSE=1