CI: Set temporary directory for tests.

Hopefully this avoids the mismatched directories with saving into a user temporary directory with one user name and reading from a user temporary directory with a different user name.

Author: DWesl

.github/workflows/cygwin-test.yml

@@ -14,6 +14,8 @@ jobs:
     env:
       CHERE_INVOKING: 1
       SHELLOPTS: igncr
+      TMP: "/tmp"
+      TEMP: "/tmp"
 
     steps:
     - name: Force LF line endings