Fix: symlink bin/arm directory is not handled correctly

This change fixes a bug that a symlink in the bin/* directory of an APEX
is not added to the fs_config file.

Bug: 137918291
Test: choosecombo aosp_x86_arm
TARGET_FLATTEN_APEX=false m com.android.runtime.debug is successful

Change-Id: Ib10b635f08e03b18e8ad5407d8de6bac2c85326d
diff --git a/apex/apex.go b/apex/apex.go
index 284af5c..ba73163 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -1009,7 +1009,7 @@
 			if f.installDir == "bin" || strings.HasPrefix(f.installDir, "bin/") {
 				executablePaths = append(executablePaths, pathInApex)
 				for _, s := range f.symlinks {
-					executablePaths = append(executablePaths, filepath.Join("bin", s))
+					executablePaths = append(executablePaths, filepath.Join(f.installDir, s))
 				}
 			} else {
 				readOnlyPaths = append(readOnlyPaths, pathInApex)