Merge #20353: configure: Support -fdebug-prefix-map and -fmacro-prefix-map

7abac98d3e configure: Support -f{debug,macro}-prefix-map (Anthony Towns)

Pull request description:

  When bitcoin is checked out in two directories (eg via git worktree) object files between the two will differ due to the full path being included in the debug section. `-fdebug-prefix-map` is used to replace this with "." to avoid this unnecessary difference and allow ccache to share objects between worktrees (provided the source and compile options are the same).

  Also provide `-fmacro-prefix-map` if supported so that the working dir is not encoded in `__FILE__` macros.

ACKs for top commit:
  practicalswift:
    cr ACK 7abac98d3e3c1bc8ad66cb5c05184b9c5cc674d5: patch looks correct
  fanquake:
    ACK 7abac98d3e

Tree-SHA512: b6a37c1728ec3b2e552f244da0e66db113c1e7662c7ac502e12ff466f3dbfbfefae12695ca135137c50dbb1c4c5d84059116c0cd09b391a17466dc77b8726679

configure.ac

@@ -1640,6 +1640,10 @@ if test "x$use_ccache" != "xno"; then
     CXX="$ac_cv_path_CCACHE $CXX"
   fi
   AC_MSG_RESULT($use_ccache)
+  if test "x$use_ccache" = "xyes"; then
+    AX_CHECK_COMPILE_FLAG([-fdebug-prefix-map=A=B],[DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -fdebug-prefix-map=\$(abs_srcdir)=."],,[[$CXXFLAG_WERROR]])
+    AX_CHECK_PREPROC_FLAG([-fmacro-prefix-map=A=B],[DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -fmacro-prefix-map=\$(abs_srcdir)=."],,[[$CXXFLAG_WERROR]])
+  fi
 fi
 
 dnl enable wallet