This patch fixes an issue where Blender 3.5 alpha with the Metal GPU backend enabled on Japanese macOS fails to compile shaders and crashes on startup.
In a Japanese environment, `defaultCStringEncoding` is the legacy MacJapanese encoding, and it erroneously converts backslashes (0x5c) to Yen symbols (¥).
Therefore, Metal shader compile fails with the following log and Blender crashes.
```
2022-12-29 13:50:10.200 Blender[13404:246707] Compile Error - Metal Shader Library (Stage: 0), error Error Domain=MTLLibraryErrorDomain Code=3 "program_source:225:74: error: non-ASCII characters are not allowed outside of literals and identifiers
template<typename T, access A = access::sample> struct STRUCT_NAME { ¥
^
program_source:226:14: error: no template named 'TEX_TYPE'
thread TEX_TYPE<T, A> *texture; ¥
^
program_source:226:39: error: non-ASCII characters are not allowed outside of literals and identifiers
thread TEX_TYPE<T, A> *texture; ¥
^
program_source:227:29: error: non-ASCII characters are not allowed outside of literals and identifiers
thread sampler *samp; ¥
^
...
```
We can use `stringWithUTF8String` instead.
Reviewed By: fclem, MichaelPW
Differential Revision: https://developer.blender.org/D16881
48b82a6ea3