Allowlist //system/apex.

This bp2builds the one cc_binary in that package that uses
library_linking_strategy_cc_defaults. That target is buildable, but
there's still a bp2build_available allowlist bug that causes the select
statements and static_libs deps to not show up for the target (only
dynamic_deps are), due to how bp2build_available is special cased for
soong_config_module_type in the loadhook.

Test: b build //system/apex:library_linking_strategy_sample_binary
Change-Id: Ic38a1bfaa476108db63348d030e196d8561300ca
diff --git a/android/bazel.go b/android/bazel.go
index 32a55ee..f4686a0 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -245,6 +245,7 @@
 		"packages/modules/adb/proto":                         Bp2BuildDefaultTrueRecursively,
 		"packages/modules/adb/tls":                           Bp2BuildDefaultTrueRecursively,
 		"prebuilts/clang/host/linux-x86":                     Bp2BuildDefaultTrueRecursively,
+		"system/apex":                                        Bp2BuildDefaultTrue,
 		"system/core/diagnose_usb":                           Bp2BuildDefaultTrueRecursively,
 		"system/core/libasyncio":                             Bp2BuildDefaultTrue,
 		"system/core/libcrypto_utils":                        Bp2BuildDefaultTrueRecursively,