less verbose compiler command lines during build

If using hints file sys/unix/hints/linux.370 or sys/unix/hints/macOS.370
allow the majority of the boilerplate compile switches to reside in a
compiler response file, instead of on the command line.

Include one of the following on your make command line:

make response=1
  or
make resp=1

It can be combined with other make command line options. See
sys/unix/README-hints for further information about those.

The response files that it uses are:
    CC   (clang or gcc)    src/nethack_cc.rsp
    CXx  (clang++ or g++)  src/nethack_cxx.rsp

Note: I think the reduced clutter should actually become the default,
and the override should be noresponse=1 to NOT use it, but I'm
not sure how others feel, so for now, it requires
    make resp=1
Feedback on whether that should become the default or not
is welcome.

Tested on Linux with gcc-15 and on Linux with clang-20.

I haven't had a chance to test it on macOS yet.

sys/unix/README-hints

@@ -49,7 +49,10 @@ make musl=1                   Build with settings appropriate for linking with
                               musl libc, instead of glibc. This causes
                               NOCRASHREPORT to be defined, and avoids the use
                               of 'col' during the build.
-
+make resp=1                   Place the majority of the compiler switches into
+                              a response file to de-clutter the build compiler
+                              command lines and eliminate some of the
+                              unsightly wrapping that occurs.
 make CROSS_TO_MSDOS=1 package Cross-compile for an MSDOS target package.
 make CROSS_TO_WASM=1          Cross-compile for a WASM target.
 make CROSS_TO_MIPS=1          Cross-compile for a mips target.