Cannot build `nanopb`

Hey esteemed `PodToBUILD` authors,

I get the following errors when attempting to build [`nanopb`](https://github.com/nanopb/nanopb):
```
ERROR: /Volumes/.../Vendor/nanopb/BUILD.bazel:112:13: in non_arc_srcs attribute of objc_library rule //Vendor/nanopb:nanopb: source file '//Vendor/nanopb:pb_common.c' is misplaced here (expected .m or .mm)
ERROR: /Volumes/.../Vendor/nanopb/BUILD.bazel:112:13: in non_arc_srcs attribute of objc_library rule //Vendor/nanopb:nanopb: '//Vendor/nanopb:pb_common.c' does not produce any objc_library non_arc_srcs files (expected .m or .mm)
ERROR: /Volumes/.../Vendor/nanopb/BUILD.bazel:112:13: in non_arc_srcs attribute of objc_library rule //Vendor/nanopb:nanopb: source file '//Vendor/nanopb:pb_decode.c' is misplaced here (expected .m or .mm)
ERROR: /Volumes/.../Vendor/nanopb/BUILD.bazel:112:13: in non_arc_srcs attribute of objc_library rule //Vendor/nanopb:nanopb: '//Vendor/nanopb:pb_decode.c' does not produce any objc_library non_arc_srcs files (expected .m or .mm)
ERROR: /Volumes/.../Vendor/nanopb/BUILD.bazel:112:13: in non_arc_srcs attribute of objc_library rule //Vendor/nanopb:nanopb: source file '//Vendor/nanopb:pb_encode.c' is misplaced here (expected .m or .mm)
ERROR: /Volumes/.../Vendor/nanopb/BUILD.bazel:112:13: in non_arc_srcs attribute of objc_library rule //Vendor/nanopb:nanopb: '//Vendor/nanopb:pb_encode.c' does not produce any objc_library non_arc_srcs files (expected .m or .mm)
```

From the following declaration:
```
new_pod_repository(
name = "nanopb",
url = "https://github.com/nanopb/nanopb/archive/df0e92f474f9cca704fe2b31483f0b4d1b1715a4.zip",
podspec_url = "https://raw.githubusercontent.com/CocoaPods/Specs/master/Specs/6/1/e/nanopb/1.30905.0/nanopb.podspec.json",
inhibit_warnings = True,
)
```