meson: only run symbols-check if nm is available

And drop the redundant check from symbols-check.py, which was actually
masking all kinds of issues.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35891>

bin/symbols-check.py

@@ -141,7 +141,6 @@ def main():
                         help='do not process this symbol')
     args = parser.parse_args()
 
-    try:
     if platform.system() == 'Windows':
         if not args.dumpbin:
             parser.error('--dumpbin is mandatory')
@@ -150,10 +149,7 @@ def main():
         if not args.nm:
             parser.error('--nm is mandatory')
         lib_symbols = get_symbols_nm(args.nm, args.lib)
-    except:
-        # We can't run this test, but we haven't technically failed it either
-        # Return the GNU "skip" error code
-        exit(77)
+
     mandatory_symbols = []
     optional_symbols = []
     with open(args.symbols_file) as symbols_file:

meson.build

@@ -2233,7 +2233,7 @@ if host_machine.system() == 'windows'
   endif
 else
   prog_nm = find_program('nm')
-  with_symbols_check = with_tests
+  with_symbols_check = prog_nm.found() and with_tests
   symbols_check_args = ['--nm', prog_nm.full_path()]
 endif