autoconf: fix for long perl shebangs with autoconf@2.70+ (#34331)

autoconf 2.70 uses use warnings instead of -w so that PERL=/usr/bin/env perl can be passed, but we want to fix absolute paths anyhow through sbang upon install. So, we stick to patching the one perl script that's used during the build.

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

@@ -83,7 +83,11 @@ def patch(self):
         # We save and restore the modification timestamp of the file to prevent
         # regeneration of the respective man page:
         with keep_modification_time(patched_file):
-            filter_file("^#! @PERL@ -w", "#! /usr/bin/env perl", patched_file)
+            if "@2.70:" in self.spec:
+                shebang_string = "^#! @PERL@"
+            else:
+                shebang_string = "^#! @PERL@ -w"
+            filter_file(shebang_string, "#! /usr/bin/env perl", patched_file)
         if self.version == Version("2.62"):
             # skip help2man for patched autoheader.in and autoscan.in
             touch("man/autoheader.1")
@@ -99,10 +103,15 @@ def filter_sbang(self):
         # target will try to rebuild the binaries (filter_file updates the
         # timestamps)
 
+        if "@2.70:" in self.spec:
+            shebang_string = "#! {0}"
+        else:
+            shebang_string = "#! {0} -w"
+
         # Revert sbang, so Spack's sbang hook can fix it up
         filter_file(
             "^#! /usr/bin/env perl",
-            "#! {0} -w".format(self.spec["perl"].command.path),
+            shebang_string.format(self.spec["perl"].command.path),
             self.prefix.bin.autom4te,
             backup=False,
         )