crtbegin: eliminate duplicate code

crtbegin_dynamic and crtbegin_static are essentially identical,
minus a few trivial differences (comments and whitespace).

Eliminate duplicates.

Change-Id: Ic9fae6bc9695004974493b53bfc07cd3bb904480
diff --git a/libc/Android.mk b/libc/Android.mk
index 0dbc0be..77da9c8 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -574,13 +574,13 @@
 
 
 GEN := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)/crtbegin_static.o
-$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin_static.S
+$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin.S
 	@mkdir -p $(dir $@)
 	$(TARGET_CC) $(libc_crt_target_cflags) -o $@ -c $<
 ALL_GENERATED_SOURCES += $(GEN)
 
 GEN := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)/crtbegin_dynamic.o
-$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin_dynamic.S
+$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin.S
 	@mkdir -p $(dir $@)
 	$(TARGET_CC) $(libc_crt_target_cflags) -o $@ -c $<
 ALL_GENERATED_SOURCES += $(GEN)