[tools] Fix compiler test to work on macOS.

Author: neboat

tools/build

@@ -128,20 +128,22 @@ cmake --build . -- -j "${NCPU}"
 # TODO: cmake --install ...
 
 # Verify that the compiler works.
-cat <<CPP > ${tempfile:=$(mktemp -t XXXXXX.cpp)}
+tempdir=$(mktemp -d)
+tempfile="${tempdir}/tmp.cpp"
+cat > ${tempfile} <<CPP
 #include <cstdio>
 int main() {
     printf("Hello, world\n");
     return 0;
 }
 CPP
-if ! ${BUILD_DIR}/bin/clang++ ${tempfile} -o temp ; then
+if ! ${BUILD_DIR}/bin/clang++ ${tempfile} -o ${tempdir}/tmp ; then
     echo -e "Failed to compile test program with OpenCilk compiler.\nThere might be a problem with your system configuration.\nOutput of '${BUILD_DIR}/bin/clang++ -v':"
     ${BUILD_DIR}/bin/clang++ -v
-    rm -rf ${tempfile} temp
+    rm -rf ${tempdir}
     exit 1
 fi
-rm -rf ${tempfile} temp
+rm -rf ${tempdir}
 
 case "${OS}" in
     # Darwin is a special case.  The version is not embedded in the path.