allow overriding nm with NM

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>

mesonbuild/scripts/symbolextractor.py

@@ -54,13 +54,18 @@ def linux_syms(libfilename, outfilename):
         readelfbin = os.environ[evar].strip()
     else:
         readelfbin = 'readelf'
+    evar = 'NM'
+    if evar in os.environ:
+        nmbin = os.environ[evar].strip()
+    else:
+        nmbin = 'nm'
     pe = subprocess.Popen([readelfbin, '-d', libfilename], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     output = pe.communicate()[0].decode()
     if pe.returncode != 0:
         raise RuntimeError('Readelf does not work')
     result = [x for x in output.split('\n') if 'SONAME' in x]
     assert(len(result) <= 1)
-    pnm = subprocess.Popen(['nm', '--dynamic', '--extern-only', '--defined-only', '--format=posix', libfilename],
+    pnm = subprocess.Popen([nmbin, '--dynamic', '--extern-only', '--defined-only', '--format=posix', libfilename],
                            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     output = pnm.communicate()[0].decode()
     if pnm.returncode != 0: