core: Don't debug native modules when TARGET_BUILD_TYPE==debug

Don't make the simulator default to debug mode.

Remove all global "debug" {C,CPP}FLAGS, which are no longer used.
diff --git a/core/combo/linux-arm.mk b/core/combo/linux-arm.mk
index 959bd87..b0cc51c 100644
--- a/core/combo/linux-arm.mk
+++ b/core/combo/linux-arm.mk
@@ -15,32 +15,31 @@
 
 $(combo_target)NO_UNDEFINED_LDFLAGS := -Wl,--no-undefined
 
-TARGET_arm_release_CFLAGS :=    -O2 \
-                                -fomit-frame-pointer \
-                                -fstrict-aliasing    \
-                                -funswitch-loops     \
-                                -finline-limit=300
+TARGET_arm_CFLAGS :=    -O2 \
+                        -fomit-frame-pointer \
+                        -fstrict-aliasing    \
+                        -funswitch-loops     \
+                        -finline-limit=300
 
-TARGET_thumb_release_CFLAGS :=  -mthumb \
-                                -Os \
-                                -fomit-frame-pointer \
-                                -fno-strict-aliasing \
-                                -finline-limit=64
+TARGET_thumb_CFLAGS :=  -mthumb \
+                        -Os \
+                        -fomit-frame-pointer \
+                        -fno-strict-aliasing \
+                        -finline-limit=64
 
-# When building for debug, compile everything as arm.
-TARGET_arm_debug_CFLAGS := $(TARGET_arm_release_CFLAGS) -fno-omit-frame-pointer -fno-strict-aliasing
-TARGET_thumb_debug_CFLAGS := $(TARGET_thumb_release_CFLAGS) -marm -fno-omit-frame-pointer
-
-# NOTE: if you try to build a debug build with thumb, several
+# Set FORCE_ARM_DEBUGGING to "true" in your buildspec.mk
+# or in your environment to force a full arm build, even for
+# files that are normally built as thumb; this can make
+# gdb debugging easier.  Don't forget to do a clean build.
+#
+# NOTE: if you try to build a -O0 build with thumb, several
 # of the libraries (libpv, libwebcore, libkjs) need to be built
 # with -mlong-calls.  When built at -O0, those libraries are
 # too big for a thumb "BL <label>" to go from one end to the other.
-
-## As hopefully a temporary hack,
-## use this to force a full ARM build (for easier debugging in gdb)
-## (don't forget to do a clean build)
-##TARGET_arm_release_CFLAGS := $(TARGET_arm_release_CFLAGS) -fno-omit-frame-pointer
-##TARGET_thumb_release_CFLAGS := $(TARGET_thumb_release_CFLAGS) -marm -fno-omit-frame-pointer
+ifeq ($(FORCE_ARM_DEBUGGING),true)
+  TARGET_arm_CFLAGS += -fno-omit-frame-pointer
+  TARGET_thumb_CFLAGS += -marm -fno-omit-frame-pointer
+endif
 
 ## on some hosts, the target cross-compiler is not available so do not run this command
 ifneq ($(wildcard $($(combo_target)CC)),)
diff --git a/core/combo/select.mk b/core/combo/select.mk
index c54da22..273b660 100644
--- a/core/combo/select.mk
+++ b/core/combo/select.mk
@@ -7,7 +7,6 @@
 #   $(combo_target)OS -- standard name for this host (LINUX, DARWIN, etc.)
 #   $(combo_target)ARCH -- standard name for process architecture (powerpc, x86, etc.)
 #   $(combo_target)GLOBAL_CFLAGS -- C compiler flags to use for everything
-#   $(combo_target)DEBUG_CFLAGS -- additional C compiler flags for debug builds
 #   $(combo_target)RELEASE_CFLAGS -- additional C compiler flags for release builds
 #   $(combo_target)GLOBAL_ARFLAGS -- flags to use for static linking everything
 #   $(combo_target)SHLIB_SUFFIX -- suffix of shared libraries
@@ -39,7 +38,6 @@
 
 # These flags might (will) be overridden by the target makefiles
 $(combo_target)GLOBAL_CFLAGS := -fno-exceptions -Wno-multichar
-$(combo_target)DEBUG_CFLAGS := -O0 -g
 $(combo_target)RELEASE_CFLAGS := -O2 -g -fno-strict-aliasing
 $(combo_target)GLOBAL_ARFLAGS := crs