add llvm configure flags to enable/disable target OSes/Envs

Makefile.rules

 #===-- Makefile.rules - Common make rules for LLVM ---------*- Makefile -*--===#
 #
 #                     The LLVM Compiler Infrastructure
 #
 # This file is distributed under the University of Illinois Open Source
 # License. See LICENSE.TXT for details.
 #
 #===------------------------------------------------------------------------===#
 #
 # This file is included by all of the LLVM makefiles.  For details on how to use
@@ skipping 300 matching lines @@
 endif
 
 # If ENABLE_EXPENSIVE_CHECKS=1 is specified (make command line or
 # configured), then enable expensive checks by defining the
 # appropriate preprocessor symbols.
 ifeq ($(ENABLE_EXPENSIVE_CHECKS),1)
   BuildMode := $(BuildMode)+Checks
   CPP.Defines += -D_GLIBCXX_DEBUG -DXDEBUG
 endif
 
+# Take the list of TARGET_OSES_TO_BUILD and generate preprocessor symbols
+# indicating that the target OS is enabled.
+CPP.Defines += $(patsubst %,-DLLVM_ENABLED_TARGET_OS_%,\
+        $(shell echo $(TARGET_OSES_TO_BUILD) | tr a-z A-Z))
+
+# Take the list of TARGET_ENVS_TO_BUILD and generate preprocessor symbols
+# indicating that the target environment is enabled.
+CPP.Defines += $(patsubst %,-DLLVM_ENABLED_TARGET_ENV_%,\
+        $(shell echo $(TARGET_ENVS_TO_BUILD) | tr a-z A-Z))
+
 # LOADABLE_MODULE implies several other things so we force them to be
 # defined/on.
 ifdef LOADABLE_MODULE
   SHARED_LIBRARY := 1
   LINK_LIBS_IN_SHARED := 1
 endif
 
 ifdef SHARED_LIBRARY
   ENABLE_PIC := 1
   PIC_FLAG = "(PIC)"
@@ skipping 1942 matching lines @@
         $(Echo) "ProjLibsPaths: " '$(ProjLibsPaths)'
         $(Echo) "ProjLibsOptions: " '$(ProjLibsOptions)'
 
 ###
 # Debugging
 
 # General debugging rule, use 'make dbg-print-XXX' to print the
 # definition, value and origin of XXX.
 make-print-%:
         $(error PRINT: $(value $*) = "$($*)" (from $(origin $*)))