FindBLAS: Handle Windows Intel MKLROOT with backslash

Modules/FindBLAS.cmake

@@ -473,7 +473,7 @@ if(BLA_VENDOR MATCHES "Intel" OR BLA_VENDOR STREQUAL "All")
         set(BLAS_mkl_OS_NAME "lin")
       endif()
       if(DEFINED ENV{MKLROOT})
-        set(BLAS_mkl_MKLROOT "$ENV{MKLROOT}")
+        file(TO_CMAKE_PATH "$ENV{MKLROOT}" BLAS_mkl_MKLROOT)
         # If MKLROOT points to the subdirectory 'mkl', use the parent directory instead
         # so we can better detect other relevant libraries in 'compiler' or 'tbb':
         get_filename_component(BLAS_mkl_MKLROOT_LAST_DIR "${BLAS_mkl_MKLROOT}" NAME)