msys2: Do not use snapshot.project on S3_1
As https://www.hostedredmine.com/issues/677356 said about S3_0 after it had gone to d3f:
"In a stable branch (especially after d3f) msys2 Makefile use of snapshot.project causes more problems than it provides benefits."
Drop that from S3_1.
For S3_1 only (not to master)
As https://www.hostedredmine.com/issues/677356 said about S3_0 after it had gone to d3f:
"In a stable branch (especially after d3f) msys2 Makefile use of snapshot.project causes more problems than it provides benefits."
Drop that from S3_1.