[chore] move api-diff pipeline to ubuntu runner (open-telemetry#12549)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Move the api-diff workflow to the standard `ubuntu-latest` runner and
adjust the OS dependent call to mktemp so that it works for both linux
and macos.

<!-- Issue number if applicable -->
#### Link to tracking issue
Fixes
open-telemetry#7444

#### Testing

Tested on my fork:

https://github.com/mowies/opentelemetry-collector/actions/runs/13941800348/job/39019991437

Also tested this locally on MacOS.



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---------

Signed-off-by: Moritz Wiesinger <[email protected]>

Author: mowies

.github/workflows/api-compatibility.yml

@@ -14,7 +14,7 @@ permissions: read-all
 
 jobs:
   Check-Compatibility:
-    runs-on: macos-latest
+    runs-on: ubuntu-latest
     env:
       BASE_REF: ${{ github.base_ref }}
       HEAD_REF: ${{ github.head_ref }}

internal/buildscripts/gen-apidiff.sh

@@ -45,7 +45,8 @@ fi
 set -ex
 
 # Create temp dir for generated files.
-tmp_dir=$(mktemp -d -t apidiff)
+# Source: https://unix.stackexchange.com/a/84980
+tmp_dir=$(mktemp -d 2>/dev/null || mktemp -d -t 'apidiff')
 clean_up() {
     ARG=$?
     if [ $dry_run = true ]; then