ChangeLog:

PR target/37137
* Makefile.def (flags_to_pass): Remove redundant and incomplete
STAGE1_CFLAGS, STAGE2_CFLAGS, STAGE3_CFLAGS, and STAGE4_CFLAGS.
Add FLAGS_FOR_TARGET and BUILD_CONFIG.
(bootstrap_stage): Remove bootstrap-debug custom stages.  Turn
stage_configureflags, stage_cflags and stage_libcflags into
explicit Makefile macros.
* Makefile.tpl (HOST_EXPORTS, EXTRA_HOST_FLAGS): Pass GCJ and
GFORTRAN.
(POSTSTAGE1_HOST_EXPORTS): Add XGCC_FLAGS_FOR_TARGET and TFLAGS to
CC.  Set CC_FOR_BUILD from CC.
(BASE_TARGET_EXPORTS, RAW_CXX_TARGET_EXPORTS,
NORMAL_TARGET_EXPORTS): Move SYSROOT_CFLAGS_FOR_TARGET and
DEBUG_PREFIX_CFLAGS_FOR_TARGET from CFLAGS and CXXFLAGS to
XGCC_FLAGS_FOR_TARGET.  Add it along with TFLAGS to CC, CXX, GCJ,
and GFORTRAN.
(TFLAGS, STAGE_CFLAGS, STAGE_TFLAGS, STAGE_CONFIGURE_FLAGS): New.
(_LIBCFLAGS): Renamed to _TFLAGS.
(do-compare-debug, do-compare3-debug): Drop.
(CC, GCC_FOR_TARGET, CXX_FOR_TARGET, RAW_CXX_FOR_TARGET,
GCJ_FOR_TARGET, GFORTRAN_FOR_TARGET): Remove FLAGS_FOR_TARGET.
(FLAGS_FOR_TARGET, SYSROOT_CFLAGS_FOR_TARGET,
DEBUG_PREFIX_CFLAGS_FOR_TARGET): Move down.
(XGCC_FLAGS_FOR_TARGET): New.
(BASE_FLAGS_TO_PASS): Pass STAGEid_CFLAGS, STAGEid_TFLAGS and TFLAGS.
(EXTRA_HOST_FLAGS): Pass GCJ and GFORTRAN.
(POSTSTAGE1_FLAGS_TO_PASS): Move SYSROOT_CFLAGS_FOR_TARGET and
DEBUG_PREFIX_CFLAGS_FOR_TARGET from CFLAGS, CXXFLAGS, LIBCFLAGS,
LIBCXXFLAGS to XGCC_FLAGS_FOR_TARGET.    Add it along with TFLAGS
to CC, CXX, GCJ, and GFORTRAN.  Pass XGCC_FLAGS_FOR_TARGET and
TFLAGS.
(BUILD_CONFIG): Include if requested.
(all): Set TFLAGS on bootstrap.
(configure-stageid-prefixmodule): Pass TFLAGS, adjust FLAGS.
(all-stageid-prefixmodule): Likewise.
(do-clean, distclean-stageid): Set TFLAGS.
(restrap): Fix whitespace.
* Makefile.in: Rebuilt.
config/ChangeLog:
* multi.m4: Save CXX, GFORTRAN and GCJ in config.status.
* mt-gnu (CXXFLAGS_FOR_TARGET): Adjust.
* bootstrap-O1.mk: New.
* bootstrap-O3.mk: New.
* bootstrap-debug.mk: New.