Save deps when asflags contains -xassembler-with-cpp

Usually, ".S" files are processes with the c preprocessor, and ".s"
files are not, so they don't have any dependency information, since it
is generated by the preprocessor.

But with the -xassembler-with-cpp flag, ".s" files are processed with
the preprocessor, so we should ask for dependency information from them.

Test: NINJA_ARGS="-t deps out/soong/.intermediates/external/sonivox/arm-wt-22k/libsonivox/android_arm_armv7-a-neon_core_static/obj/external/sonivox/arm-wt-22k/lib_src/ARM-E_filter_gnu.o" m
Test: treehugger
Change-Id: Iee7baeebc2b205b5a2f33e7c1705ea4a5b4fc95a