configure: Support -f{debug,macro}-prefix-map

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.

Author: ajtowns

configure.ac

@@ -1496,6 +1496,10 @@ 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