FindLAPACK: Distinguish check result variable name from FindBLAS
Since commit 192a9182, FindLAPACK accidentally used FindBLAS's
BLAS_ prefix for some of its check results.
Since !2312 (merged), FindBLAS stores a check result in a plain
BLAS_WORKS variable. The typo in FindLAPACK happens to cause a collision with that name.
The typo was already fixed in post-3.13 development as part of other work in !2633 (merged). Fix the typo in the 3.13 version of FindLAPACK to avoid the collision. Otherwise it could cause FindLAPACK to incorrectly determine that a certain library combination does not work (or incrrectly that it works).
Fixes: #18860 (closed)