m4 package: only apply nvhpc.patch for version 1.4.18 (#24730)
m4 package: only apply nvhpc.patch for version 1.4.18 (#24730)

The patch as-is does not apply to 1.4.19
LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack