librust_baremetal: Add strtol

Add strtol (required by libfdt), which only depends on libc functions
the library already provides or requires.

Bug: 232900974
Test: m pvmfw_bin # with aosp/2314779
Change-Id: I460571b64369c6bf45fef213252f305e978c694d
diff --git a/libc/Android.bp b/libc/Android.bp
index 864090b..f50d440 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -2280,6 +2280,7 @@
     ],
     srcs: [
         "bionic/fortify.cpp",
+        "bionic/strtol.cpp",
     ],
     arch: {
         arm64: {