configure: Pass CPPFLAGS_FOR_BUILD to subdirs

Because CPPFLAGS_FOR_BUILD is used in some subdirectories (through
bfd/warning.m4), not AC_SUBSTing the variable causes minor issues.

Fortunately, it didn't cause severe errors but error messages related to
@CPPFLAGS_FOR_BUILD@ (not AC_SUBSTed CPPFLAGS_FOR_BUILD variable passed
to subdirectories through Makefile) remain in config.log.

To avoid invalid invocation of preprocessor for build environment, we
need to set proper CPPFLAGS_FOR_BUILD (may be empty) and pass it to
subdirectories that need it.  This is what this commit does.

ChangeLog:

	* configure.ac: Pass CPPFLAGS_FOR_BUILD to subdirectories.
	* configure: Regenerate.

configure

@@ -651,6 +651,7 @@ GFORTRAN_FOR_BUILD
 DLLTOOL_FOR_BUILD
 CXX_FOR_BUILD
 CXXFLAGS_FOR_BUILD
+CPPFLAGS_FOR_BUILD
 CFLAGS_FOR_BUILD
 CC_FOR_BUILD
 AS_FOR_BUILD
@@ -8024,6 +8025,7 @@ esac
 # our build compiler if desired.
 if test x"${build}" = x"${host}" ; then
   CFLAGS_FOR_BUILD=${CFLAGS_FOR_BUILD-${CFLAGS}}
+  CPPFLAGS_FOR_BUILD=${CPPFLAGS_FOR_BUILD-${CPPFLAGS}}
   CXXFLAGS_FOR_BUILD=${CXXFLAGS_FOR_BUILD-${CXXFLAGS}}
   LDFLAGS_FOR_BUILD=${LDFLAGS_FOR_BUILD-${LDFLAGS}}
 fi
@@ -8102,6 +8104,7 @@ done
 
 
 
+
 # Generate default definitions for YACC, M4, LEX and other programs that run
 # on the build machine.  These are used if the Makefile can't locate these
 # programs in objdir.

configure.ac

@@ -3326,6 +3326,7 @@ esac
 # our build compiler if desired.
 if test x"${build}" = x"${host}" ; then
   CFLAGS_FOR_BUILD=${CFLAGS_FOR_BUILD-${CFLAGS}}
+  CPPFLAGS_FOR_BUILD=${CPPFLAGS_FOR_BUILD-${CPPFLAGS}}
   CXXFLAGS_FOR_BUILD=${CXXFLAGS_FOR_BUILD-${CXXFLAGS}}
   LDFLAGS_FOR_BUILD=${LDFLAGS_FOR_BUILD-${LDFLAGS}}
 fi
@@ -3392,6 +3393,7 @@ AC_SUBST(AR_FOR_BUILD)
 AC_SUBST(AS_FOR_BUILD)
 AC_SUBST(CC_FOR_BUILD)
 AC_SUBST(CFLAGS_FOR_BUILD)
+AC_SUBST(CPPFLAGS_FOR_BUILD)
 AC_SUBST(CXXFLAGS_FOR_BUILD)
 AC_SUBST(CXX_FOR_BUILD)
 AC_SUBST(DLLTOOL_FOR_BUILD)