Add /system_ext/bin to shell search path

/system_ext/bin has executable binaries. They must be in the shell
search path.

Bug: 134909174
Bug: 134359158
Test: check PATH in the adb shell
Change-Id: I997a2347fa85c444f2e335bede0d63b7703ba001
diff --git a/libc/include/paths.h b/libc/include/paths.h
index 0aa4d93..cfbc5b3 100644
--- a/libc/include/paths.h
+++ b/libc/include/paths.h
@@ -47,7 +47,7 @@
 #define _PATH_CONSOLE "/dev/console"
 
 /** Default shell search path. */
-#define _PATH_DEFPATH "/product/bin:/apex/com.android.runtime/bin:/apex/com.android.art/bin:/system/bin:/system/xbin:/odm/bin:/vendor/bin:/vendor/xbin"
+#define _PATH_DEFPATH "/product/bin:/apex/com.android.runtime/bin:/apex/com.android.art/bin:/system_ext/bin:/system/bin:/system/xbin:/odm/bin:/vendor/bin:/vendor/xbin"
 
 /** Path to the directory containing device files. */
 #define _PATH_DEV "/dev/"