fix cmake not finding openblas

dlib/cmake_utils/find_blas.cmake

@@ -70,8 +70,8 @@ if (UNIX OR MINGW)
    pkg_check_modules(LAPACK_REFERENCE lapack)
    # Make sure the cblas found by pkgconfig actually has cblas symbols.
    SET(CMAKE_REQUIRED_LIBRARIES "${BLAS_REFERENCE_LDFLAGS}")   
-   CHECK_FUNCTION_EXISTS(cblas_ddot HAVE_CBLAS)
-   if (BLAS_REFERENCE_FOUND AND LAPACK_REFERENCE_FOUND AND HAVE_CBLAS)
+   CHECK_FUNCTION_EXISTS(cblas_ddot PKGCFG_HAVE_CBLAS)
+   if (BLAS_REFERENCE_FOUND AND LAPACK_REFERENCE_FOUND AND PKGCFG_HAVE_CBLAS)
       set(blas_libraries "${BLAS_REFERENCE_LDFLAGS}")
       set(lapack_libraries "${LAPACK_REFERENCE_LDFLAGS}")
       set(blas_found 1)
@@ -283,8 +283,8 @@ if (UNIX OR MINGW)
    # with it.  But it's fine since the MKL should always have cblas.
    if (blas_found AND NOT found_intel_mkl)
       set(CMAKE_REQUIRED_LIBRARIES ${blas_libraries})
-      CHECK_FUNCTION_EXISTS(cblas_ddot HAVE_CBLAS)
-      if (NOT HAVE_CBLAS)
+      CHECK_FUNCTION_EXISTS(cblas_ddot FOUND_BLAS_HAS_CBLAS)
+      if (NOT FOUND_BLAS_HAS_CBLAS)
          message(STATUS "BLAS library does not have cblas symbols, so dlib will not use BLAS or LAPACK")
          set(blas_found 0)
          set(lapack_found 0)
@@ -400,8 +400,8 @@ elseif(WIN32 AND NOT MINGW)
       # the compiler we are using.  One way to do this check is to see if we can
       # link to it right now.
       set(CMAKE_REQUIRED_LIBRARIES ${blas_libraries})
-      CHECK_FUNCTION_EXISTS(cblas_ddot HAVE_CBLAS)
-      if (NOT HAVE_CBLAS)
+      CHECK_FUNCTION_EXISTS(cblas_ddot MKL_HAS_CBLAS)
+      if (NOT MKL_HAS_CBLAS)
          message("BLAS library does not have cblas symbols, so dlib will not use BLAS or LAPACK")
          set(blas_found 0)
          set(lapack_found 0)