Nirbheek Chauhan 8e1b6accbd meson: Always use forward slashes in defines with paths
Fixes the following build failure on MSYS2:

```
../subprojects/gstreamer/tests/check/elements/filesrc.c: In function 'test_seeking':
../subprojects/gstreamer/tests/check/elements/filesrc.c:107:53: error: incomplete universal character name \U
  107 |   g_object_set (G_OBJECT (src), "location", TESTFILE, NULL);
      |                                                     ^
../subprojects/gstreamer/tests/check/elements/filesrc.c:107:53: warning: unknown escape sequence: '\A'
../subprojects/gstreamer/tests/check/elements/filesrc.c:107:53: warning: unknown escape sequence: '\g'
../subprojects/gstreamer/tests/check/elements/filesrc.c:107:53: warning: unknown escape sequence: '\s'
../subprojects/gstreamer/tests/check/elements/filesrc.c:107:53: warning: unknown escape sequence: '\g'
../subprojects/gstreamer/tests/check/elements/filesrc.c:107:53: warning: unknown escape sequence: '\c'
```

Due to: `-DTESTFILE=\"C:\\Users\\Administrator\[...]`

https://gitlab.freedesktop.org/nirbheek/gstreamer/-/jobs/45317733

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5018>
2023-07-12 21:17:25 +00:00
..
2022-03-01 11:33:10 +00:00
2023-01-23 19:41:07 +00:00
2023-01-23 23:04:53 +00:00
2023-01-23 19:41:07 +00:00
2023-01-23 19:41:07 +00:00