Autoreconf is necessary after patch

var/spack/repos/builtin/packages/m4/inline-pgi.patch

@@ -8,3 +8,15 @@
           && !(defined __SUNPRO_C && __STDC__))) \
       && !defined _GL_EXTERN_INLINE_STDHEADER_BUG)
  # define _GL_INLINE inline
+--- a/configure.ac
++++ b/configure.ac
+@@ -22,7 +22,7 @@
+   [bug-m4@gnu.org])
+ AC_CONFIG_AUX_DIR([build-aux])
+ 
+-AM_INIT_AUTOMAKE([1.11.6 dist-bzip2 dist-xz color-tests parallel-tests
++AM_INIT_AUTOMAKE([dist-bzip2 dist-xz color-tests parallel-tests
+ silent-rules subdir-objects gnu])
+ 
+ m4_pattern_forbid([^M4_[A-Z]])
+

var/spack/repos/builtin/packages/m4/package.py

@@ -14,6 +14,10 @@ class M4(Package):
     depends_on('libsigsegv', when='+sigsegv')
 
     def install(self, spec, prefix):
+        # After patch, update generated configuration files that depend on extern-inline.m4
+        autoreconf = which('autoreconf')
+        autoreconf()
+
         configure_args = []
         if 'libsigsegv' in spec:
             configure_args.append('--with-libsigsegv-prefix=%s' % spec['libsigsegv'].prefix)