Remove -Werror from default flags, keep it in CI

.github/workflows/scripts/build-ispc.sh

@@ -1,4 +1,4 @@
 #!/bin/bash -e
 echo PATH=$PATH
-cmake -B build -DISPC_PREPARE_PACKAGE=ON -DISPC_INCLUDE_BENCHMARKS=ON
+cmake -B build -DISPC_PREPARE_PACKAGE=ON -DISPC_INCLUDE_BENCHMARKS=ON -DCMAKE_CXX_FLAGS=-Werror
 cmake --build build --target package -j4

CMakeLists.txt

@@ -430,7 +430,7 @@ if (MSVC)
     set_source_files_properties(${FLEX_OUTPUT} PROPERTIES COMPILE_FLAGS "/wd4005 /wd4003")
     set_source_files_properties(${BISON_OUTPUT} PROPERTIES COMPILE_FLAGS "/wd4005 /wd4065")
 else()
-    target_compile_options(${PROJECT_NAME} PRIVATE -Wall -Wno-sign-compare -Wno-unused-function -Werror ${LLVM_CPP_FLAGS})
+    target_compile_options(${PROJECT_NAME} PRIVATE -Wall -Wno-sign-compare -Wno-unused-function ${LLVM_CPP_FLAGS})
     # The change implementing -Wno-unused-but-set-variable in clang was reverted, so commenting out for now.
     #if (${LLVM_VERSION_NUMBER} VERSION_GREATER_EQUAL "13.0.0")
     #    set_source_files_properties(${BISON_CPP_OUTPUT} PROPERTIES COMPILE_FLAGS "-Wno-unused-but-set-variable")

docker/ubuntu/cpu_ispc_build/Dockerfile

@@ -61,7 +61,7 @@ RUN apt-get -y update && apt-get install -y m4 bison flex zlib1g-dev libc6-dev-i
 # Configure ISPC build
 RUN mkdir build_$LLVM_VERSION
 WORKDIR build_$LLVM_VERSION
-RUN cmake ../ -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_INSTALL_PREFIX=/usr/local/src/ispc/bin-$LLVM_VERSION
+RUN cmake ../ -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_INSTALL_PREFIX=/usr/local/src/ispc/bin-$LLVM_VERSION -DCMAKE_CXX_FLAGS=-Werror
 
 # Build ISPC
 RUN make ispc -j8 && make check-all && make install