Wrap getenv when linking a coverage-enabled binary

The wrapper to getenv() appends the effective userid (euid) of the
current process to GCOV_PREFIX.  This avoids conflicts and permissions
issues when multiple processes try to create/access the same directories
and files under /data/misc/trace.

Test: Verify that coverage files are written to
/data/misc/trace/<euid>/proc/... instead of /data/misc/trace/proc/...

Change-Id: If58081a12b2b9bc40cfcbf64c99beafe198d07af

cc/coverage.go

@@ -116,6 +116,8 @@ func (cov *coverage) flags(ctx ModuleContext, flags Flags, deps PathDeps) (Flags
 
 		coverage := ctx.GetDirectDepWithTag(getProfileLibraryName(ctx), coverageDepTag).(*Module)
 		deps.WholeStaticLibs = append(deps.WholeStaticLibs, coverage.OutputFile().Path())
+
+		flags.LdFlags = append(flags.LdFlags, "-Wl,--wrap,getenv")
 	}
 
 	return flags, deps