BPF: rename bpf_defaults to bpf_cc_defaults

With the addition of defaults to the bpf soong module (see aosp/3249485
), the name `bpf_defaults` will be used to define defaults for bpf
program compilation. While there are separate soong namespaces for
module types and module names, rename the existing bpf_defaults
cc_defaults to bpf_cc_defaults for clarity.

While we're at it, add -Wextra, and cleanup unnecessary cflags in
clauses which use bpf_cc_defaults. Add -Wno-sign-compare to resolve
build issues in external test code.

Test: TH
Change-Id: Id0407f86ad50033a77a8679d465dc9412991d764
Signed-off-by: Neill Kapron <nkapron@google.com>
diff --git a/bpf/loader/Android.bp b/bpf/loader/Android.bp
index b8c0ce7..b08913a 100644
--- a/bpf/loader/Android.bp
+++ b/bpf/loader/Android.bp
@@ -33,12 +33,7 @@
 cc_binary {
     name: "netbpfload",
 
-    defaults: ["bpf_defaults"],
-    cflags: [
-        "-Wall",
-        "-Werror",
-        "-Wthread-safety",
-    ],
+    defaults: ["bpf_cc_defaults"],
     sanitize: {
         integer_overflow: true,
     },