Don't define __ARM*__ for Clang

I have a patch for Clang ready that I will upstream instead.

build/jam/ArchitectureRules

@@ -43,10 +43,7 @@ rule ArchitectureSetup architecture
 
 	local cpu = $(HAIKU_CPU_$(architecture)) ;
 	if $(cpu) = arm {
-		if $(HAIKU_CC_IS_CLANG_$(architecture)) = 1 {
-			# Clang only defines __ARMEL__ when using -target arm-haiku-unknown
-			gccBaseFlags += -D__ARM__=1 ;
-		} else {
+		if $(HAIKU_CC_IS_CLANG_$(architecture)) != 1 {
 			# For stackcrawls - not supported by Clang
 			gccBaseFlags += -mapcs-frame ;
 		}

build/jam/board/rpi2/BoardSetup

@@ -59,9 +59,6 @@ HAIKU_BOARD_SDIMAGE_SIZE = 128 ;
 #
 
 local flags = -march=armv7-a -mfloat-abi=hard ;
-if $(HAIKU_CC_IS_CLANG_$(architecture)) = 1 {
-	flags += -D__ARM_ARCH__=7 ;
-}
 
 HAIKU_ASFLAGS_$(HAIKU_PACKAGING_ARCH) += $(flags) ;
 HAIKU_CCFLAGS_$(HAIKU_PACKAGING_ARCH) += $(flags) ;