Change check for embedded llvm version number to a regex to make test more flexible. (#79528)

This test started to fail when LLVM created the release/18.x branch and
the main branch subsequently had the version number increased from 18 to
19.

I investigated this failure (it was blocking our internal automation)
and discovered that the CHECK statement on line 27 seemed to have the
compiler version number (1800) encoded in octal that it was checking
for. I don't know if this is something that explicitly needs to be
checked, so I am leaving it in, but it should be more flexible so the
test doesn't fail anytime the version number is changed. To accomplish
that, I changed the check for the 4-digit version number to be a regex.

I originally updated this test for the 18->19 transition in
a01195f. This change makes the CHECK
line more flexible so it doesn't need to be continually updated.

Author: dyung

llvm/test/CodeGen/SystemZ/zos-ppa2.ll

@@ -24,7 +24,7 @@
 ; CHECK:    .byte   0
 ; CHECK:    .byte   3
 ; CHECK:    .short  30
-; CHECK:    .ascii  "\323\323\345\324@@@@@@\361\371\360\360\361\371\367\360\360\361\360\361\360\360\360\360\360\360\360\360"
+; CHECK:    .ascii  "\323\323\345\324@@@@@@{{((\\3[0-7]{2}){4})}}\361\371\367\360\360\361\360\361\360\360\360\360\360\360\360\360"
 define void @void_test() {
 entry:
   ret void