Export capability.h as a filegroup

... so that it can be used by fs_config_[dirs|files] genrules.
Previously, the fs_config_* were created by Android.mk and capability.h
was referenced directly from there. Since Soong doesn't allow that,
let's export the file explicitly.

Bug: 337993745
Test: m
Change-Id: I2777a4dbe6b977bc64c5f6defe748fa7993e578e
diff --git a/libc/Android.bp b/libc/Android.bp
index 84fa498..430072b 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -2990,3 +2990,8 @@
     name: "versioner-dependencies",
     srcs: ["versioner-dependencies/**/*"],
 }
+
+filegroup {
+    name: "linux_capability_header",
+    srcs: ["kernel/uapi/linux/capability.h"],
+}