Silence "arithmetic on a pointer to void is a GNU extension".

Also remove some accumulated makefile cruft.

Bug: http://b/31517901
Change-Id: I2b8dbc532bbd898c0922ffbf41dba57d8552b72a
diff --git a/Android.mk b/Android.mk
index a9b11ad..a75a812 100644
--- a/Android.mk
+++ b/Android.mk
@@ -191,29 +191,6 @@
     xattr.c \
     xmalloc.c \
 
-LOCAL_SHARED_LIBRARIES :=
-
-#    -DHAVE_DECL_PTRACE_EVENT_FORK=1 \
-    -DHAVE_DECL_PTRACE_EVENT_VFORK=1 \
-    -DHAVE_DECL_PTRACE_EVENT_CLONE=1 \
-    -DHAVE_DECL_PTRACE_EVENT_EXEC=1 \
-    -DHAVE_DECL_PTRACE_EVENT_VFORK_DONE=1 \
-    -DHAVE_DECL_PTRACE_EVENT_EXIT=1 \
-    -DHAVE_DECL_PTRACE_GETEVENTMSG=1 \
-    -DHAVE_DECL_PTRACE_GETSIGINFO=1 \
-    -DHAVE_DECL_PTRACE_O_TRACECLONE=1 \
-    -DHAVE_DECL_PTRACE_O_TRACEEXEC=1 \
-    -DHAVE_DECL_PTRACE_O_TRACEEXIT=1 \
-    -DHAVE_DECL_PTRACE_O_TRACEFORK=1 \
-    -DHAVE_DECL_PTRACE_O_TRACESYSGOOD=1 \
-    -DHAVE_DECL_PTRACE_O_TRACEVFORK=1 \
-    -DHAVE_DECL_PTRACE_SETOPTIONS=1 \
-    -UHAVE_DECL_IO_CMD_PWRITE \
-    -UHAVE_DECL_IO_CMD_PWRITEV \
-    -UHAVE_DECL_LO_FLAGS_AUTOCLEAR \
-    -UHAVE_DECL_LO_FLAGS_PARTSCAN \
-    -DHAVE_DECL_SYS_ERRLIST=1 \
-
 LOCAL_CFLAGS := \
     -DGETGROUPS_T=gid_t \
     \
@@ -337,6 +314,7 @@
     -Wwrite-strings \
     -Wsign-compare \
     -Wno-missing-field-initializers \
+    -Wno-pointer-arith \
     -Wno-unused-parameter \
     -Wno-sign-compare \