fix bash evaluation error

platforms/common/spack_utils.sh

@@ -30,7 +30,7 @@ function _install_spack() {
   if [[ $(spack compiler info ${SPACK_COMPILER}) ]]; then
     echo "Found Compiler $(spack compiler info ${SPACK_COMPILER})"
   else
-    if $(spack location --install-dir ${SPACK_COMPILER}); then
+    if [[ $(spack location --install-dir ${SPACK_COMPILER}) ]]; then
       echo "found the compiler ${SPACK_COMPILER} as a spack package at $(spack location --install-dir $SPACK_COMPILER)"
     else
       echo "could not find compiler, will now try to install it... this may take a while"