Simplify subdirectory makefiles, and be more robust by checking that they define the appropriate variables.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@93714 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/make/config.mk b/make/config.mk
index 4851191..903424d 100644
--- a/make/config.mk
+++ b/make/config.mk
@@ -11,7 +11,8 @@
 Configs := Debug Release Profile
 
 # The full list of architectures we support.
-Archs := i386 ppc x86_64 armv6 armv7
+Archs := i386 ppc x86_64
+# armv6 armv7
 
 # If TargetArch is defined, only build for that architecture (and don't use
 # -arch).
@@ -66,7 +67,7 @@
 CP := cp
 
 VERBOSE := 0
-DEBUGMAKE := 0
+DEBUGMAKE :=
 
 ###
 # Automatic and derived variables.