LTO output is not reproducible. Until it is, disable this. Sadly
there is no configuration option to do so at this time.

Upstream-Status: Pending [may be accept addition of configuration option?]
RP 2021/3/1

Index: git/configure.ac
===================================================================
--- git.orig/configure.ac
+++ git/configure.ac
@@ -124,7 +124,7 @@ AS_CASE([$CC], [*clang*],
 
 AS_CASE([$CFLAGS], [*-O[[12345sz\ ]]*],
         [CC_CHECK_FLAGS_APPEND([with_cflags], [CFLAGS], [\
-               -flto -ffat-lto-objects])],
+               ])],
         [AC_MSG_RESULT([skipping -flto, optimization not enabled])])
 AC_SUBST([OUR_CFLAGS], "$with_cflags $sanitizer_cflags")