macOS 11 version check for Perl (#19210)

* Fix 'unexpected product version' error for macOS 11.0

* Adjustment: add the minimum version that this macOS patch is necessary.

* Adding a keyword to prevent the patch being applied to systems other than darwin (macOS)

* Deleting quotation marks

var/spack/repos/builtin/packages/perl/macos-11-version-check.patch

@@ -0,0 +1,40 @@
+From 54d41b60822734cf8df543053f7bd270dfded3ed Mon Sep 17 00:00:00 2001
+From: Adam Hartley <BytesGuy@users.noreply.github.com>
+Date: Thu, 23 Jul 2020 19:53:07 +0100
+Subject: [PATCH] Future proof version check
+
+---
+ hints/darwin.sh | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/hints/darwin.sh b/hints/darwin.sh
+index 1709d224f7c..fdfbdd4a3b9 100644
+--- a/hints/darwin.sh
++++ b/hints/darwin.sh
+@@ -301,7 +301,7 @@ case "$osvers" in  # Note: osvers is the kernel version, not the 10.x
+    # We now use MACOSX_DEPLOYMENT_TARGET, if set, as an override by
+    # capturing its value and adding it to the flags.
+     case "$MACOSX_DEPLOYMENT_TARGET" in
+-    10.*)
++    [1-9][0-9].*)
+       add_macosx_version_min ccflags $MACOSX_DEPLOYMENT_TARGET
+       add_macosx_version_min ldflags $MACOSX_DEPLOYMENT_TARGET
+       ;;
+@@ -313,7 +313,7 @@ case "$osvers" in  # Note: osvers is the kernel version, not the 10.x
+ 
+ *** Unexpected MACOSX_DEPLOYMENT_TARGET=$MACOSX_DEPLOYMENT_TARGET
+ ***
+-*** Please either set it to 10.something, or to empty.
++*** Please either set it to a valid macOS version number (e.g., 10.15) or to empty.
+ 
+ EOM
+       exit 1
+@@ -327,7 +327,7 @@ EOM
+     # "ProductVersion:    10.11"     "10.11"
+         prodvers=`sw_vers|awk '/^ProductVersion:/{print $2}'|awk -F. '{print $1"."$2}'`
+     case "$prodvers" in
+-    10.*)
++    [1-9][0-9].*)
+       add_macosx_version_min ccflags $prodvers
+       add_macosx_version_min ldflags $prodvers
+       ;;

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

@@ -73,6 +73,10 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
     # https://bugzilla.redhat.com/show_bug.cgi?id=1536752
     patch('https://src.fedoraproject.org/rpms/perl/raw/004cea3a67df42e92ffdf4e9ac36d47a3c6a05a4/f/perl-5.26.1-guard_old_libcrypt_fix.patch', level=1, sha256='0eac10ed90aeb0459ad8851f88081d439a4e41978e586ec743069e8b059370ac', when='@:5.26.2')
 
+    # Fix 'Unexpected product version' error on macOS 11.0 Big Sur
+    # https://github.com/Perl/perl5/pull/17946
+    patch('macos-11-version-check.patch', when='@5.24.1:5.32.0 platform=darwin')
+
     # Installing cpanm alongside the core makes it safe and simple for
     # people/projects to install their own sets of perl modules.  Not
     # having it in core increases the "energy of activation" for doing