pkg/58900: abseil bug results in protoc header mismatch

[rnkn%rnkn.xyz@localhost]

>Number:         58900
>Category:       pkg
>Synopsis:       abseil bug results in protoc header mismatch
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Dec 13 08:15:00 +0000 2024
>Originator:     Paul W. Rankin
>Release:        pkgsrc-2024Q3
>Organization:
>Environment:
Darwin MacBookAir.home 24.1.0 Darwin Kernel Version 24.1.0: Thu Oct 10 21:05:14 PDT 2024; root:xnu-11215.41.3~2/RELEASE_ARM64_T8103 arm64

>Description:
A bug in devel/bseil fixed upstream results in build failures for packages requiring abseil and protobuf headers to match, e.g. net/mosh.

Here is the abseil bugfix: https://github.com/abseil/abseil-cpp/commit/bd0c9c58cac4463d96b574de3097422bb78215a8

This is not yet in a release. Could this be backported please?
>How-To-Repeat:
$ cd net/mosh
$ bmake install
>Fix:
$ cat > $LOCALPATCHES/devel/abseil/patch-shell-copts
diff --git a/CMake/AbseilHelpers.cmake b/CMake/AbseilHelpers.cmake
index 3c4c92fec4c..d8fb9fe5de3 100644
--- a/CMake/AbseilHelpers.cmake
+++ b/CMake/AbseilHelpers.cmake
@@ -186,15 +186,15 @@ function(absl_cc_library)
         endif()
       endif()
     endforeach()
-    set(skip_next_cflag OFF)
     foreach(cflag ${ABSL_CC_LIB_COPTS})
-      if(skip_next_cflag)
-        set(skip_next_cflag OFF)
-      elseif(${cflag} MATCHES "^-Xarch_")
+      # Strip out the CMake-specific `SHELL:` prefix, which is used to construct
+      # a group of space-separated options.
+      # https://cmake.org/cmake/help/v3.30/command/target_compile_options.html#option-de-duplication
+      string(REGEX REPLACE "^SHELL:" "" cflag "${cflag}")
+      if(${cflag} MATCHES "^-Xarch_")
         # An -Xarch_ flag implies that its successor only applies to the
-        # specified platform. Filter both of them out before the successor
-        # reaches the "^-m" filter.
-        set(skip_next_cflag ON)
+        # specified platform. Such option groups are each specified in a single
+        # `SHELL:`-prefixed string in the COPTS list, which we simply ignore.
       elseif(${cflag} MATCHES "^(-Wno-|/wd)")
         # These flags are needed to suppress warnings that might fire in our headers.
         set(PC_CFLAGS "${PC_CFLAGS} ${cflag}")

$ cd $PKGSRCDIR/devel/abseil/
$ bmake install
$ cd $PKGSRCDIR/net/mosh
$ bmake install