bpo-43109: Fix --with-lto configure option on macOS (GH-26341)

Allow --with-lto configure option to work with Apple-supplied Xcode or
Command Line Tools which do not provide llvm-ar.
(cherry picked from commit 59acfd4a09df1c141dac7845eed008af8970fce7)

Co-authored-by: Ned Deily <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/macOS/2021-05-24-21-15-41.bpo-43109.npKJ9c.rst

@@ -0,0 +1,2 @@
+Allow --with-lto configure option to work with Apple-supplied Xcode or
+Command Line Tools.

configure

@@ -7322,10 +7322,11 @@ fi
       fi
       if test "$ac_sys_system" = "Darwin" -a "${LLVM_AR_FOUND}" = "not-found"
       then
-        found_llvm_ar=`/usr/bin/xcrun -find llvm-ar 2>/dev/null`
+        # The Apple-supplied ar in Xcode or the Command Line Tools is apparently sufficient
+        found_llvm_ar=`/usr/bin/xcrun -find ar 2>/dev/null`
         if test -n "${found_llvm_ar}"
         then
-          LLVM_AR='/usr/bin/xcrun llvm-ar'
+          LLVM_AR='/usr/bin/xcrun ar'
           LLVM_AR_FOUND=found
           { printf "%s\n" "$as_me:${as_lineno-$LINENO}: llvm-ar found via xcrun: ${LLVM_AR}" >&5
 printf "%s\n" "$as_me: llvm-ar found via xcrun: ${LLVM_AR}" >&6;}
@@ -7343,6 +7344,7 @@ printf "%s\n" "$as_me: llvm-ar found via xcrun: ${LLVM_AR}" >&6;}
         Darwin*)
           # Any changes made here should be reflected in the GCC+Darwin case below
           LTOFLAGS="-flto -Wl,-export_dynamic"
+          LTOCFLAGS="-flto"
           ;;
         *)
           LTOFLAGS="-flto"
@@ -7353,6 +7355,7 @@ printf "%s\n" "$as_me: llvm-ar found via xcrun: ${LLVM_AR}" >&6;}
       case $ac_sys_system in
         Darwin*)
           LTOFLAGS="-flto -Wl,-export_dynamic"
+          LTOCFLAGS="-flto"
           ;;
         *)
           LTOFLAGS="-flto -fuse-linker-plugin -ffat-lto-objects -flto-partition=none"
@@ -7368,7 +7371,7 @@ printf "%s\n" "$as_me: llvm-ar found via xcrun: ${LLVM_AR}" >&6;}
       LTOFLAGS="$LTOFLAGS -g"
   fi
 
-  CFLAGS_NODIST="$CFLAGS_NODIST $LTOFLAGS"
+  CFLAGS_NODIST="$CFLAGS_NODIST ${LTOCFLAGS-$LTOFLAGS}"
   LDFLAGS_NODIST="$LDFLAGS_NODIST $LTOFLAGS"
 fi
 

configure.ac

@@ -1385,10 +1385,11 @@ if test "$Py_LTO" = 'true' ; then
       fi
       if test "$ac_sys_system" = "Darwin" -a "${LLVM_AR_FOUND}" = "not-found"
       then
-        found_llvm_ar=`/usr/bin/xcrun -find llvm-ar 2>/dev/null`
+        # The Apple-supplied ar in Xcode or the Command Line Tools is apparently sufficient
+        found_llvm_ar=`/usr/bin/xcrun -find ar 2>/dev/null`
         if test -n "${found_llvm_ar}"
         then
-          LLVM_AR='/usr/bin/xcrun llvm-ar'
+          LLVM_AR='/usr/bin/xcrun ar'
           LLVM_AR_FOUND=found
           AC_MSG_NOTICE([llvm-ar found via xcrun: ${LLVM_AR}])
         fi
@@ -1405,6 +1406,7 @@ if test "$Py_LTO" = 'true' ; then
         Darwin*)
           # Any changes made here should be reflected in the GCC+Darwin case below
           LTOFLAGS="-flto -Wl,-export_dynamic"
+          LTOCFLAGS="-flto"
           ;;
         *)
           LTOFLAGS="-flto"
@@ -1415,6 +1417,7 @@ if test "$Py_LTO" = 'true' ; then
       case $ac_sys_system in
         Darwin*)
           LTOFLAGS="-flto -Wl,-export_dynamic"
+          LTOCFLAGS="-flto"
           ;;
         *)
           LTOFLAGS="-flto -fuse-linker-plugin -ffat-lto-objects -flto-partition=none"
@@ -1430,7 +1433,7 @@ if test "$Py_LTO" = 'true' ; then
       LTOFLAGS="$LTOFLAGS -g"
   fi
 
-  CFLAGS_NODIST="$CFLAGS_NODIST $LTOFLAGS"
+  CFLAGS_NODIST="$CFLAGS_NODIST ${LTOCFLAGS-$LTOFLAGS}"
   LDFLAGS_NODIST="$LDFLAGS_NODIST $LTOFLAGS"
 fi