android: fix libz dynamic library dependencies

Fixes a series of libz related building errors:

target SharedLib: gallium_dri_32
(out/target/prod...SHARED_LIBRARIES/gallium_dri_intermediates/LINKED/gallium_dri.so)
external/elfutils/libelf/elf_compress.c:117: error: undefined reference to 'deflateInit_'
...
external/elfutils/libelf/elf_compress.c:244: error: undefined reference to 'inflateEnd'
clang++: error: linker command failed with exit code 1 (use -v to see
invocation)

Fixes: 85a9b1b "util/disk_cache: compress individual cache entries"
diff --git a/Android.common.mk b/Android.common.mk
index 611162a..04045bd 100644
--- a/Android.common.mk
+++ b/Android.common.mk
@@ -125,3 +125,5 @@
 
 # Quiet down the build system and remove any .h files from the sources
 LOCAL_SRC_FILES := $(patsubst %.h, , $(LOCAL_SRC_FILES))
+
+LOCAL_SHARED_LIBRARIES += libz