FindBLAS: use unset instead of set for empty variables
diff --git a/Modules/FindBLAS.cmake b/Modules/FindBLAS.cmake
index 29150c1..799d179 100644
--- a/Modules/FindBLAS.cmake
+++ b/Modules/FindBLAS.cmake
@@ -759,7 +759,7 @@
       ""
       )
   endif()
-  set(_blas_armpl_lib)
+  unset(_blas_armpl_lib)
 endif()
 
 # FLAME's blis library? (https://github.com/flame/blis)
@@ -1109,7 +1109,7 @@
       ""
       )
   endif()
-  set(_blas_eml_lib)
+  unset(_blas_eml_lib)
 endif()
 
 # Fujitsu SSL2 Library?