gnu: openblas-ilp64: Add symbol suffix.

* gnu/packages/maths.scm (openblas-ilp64)[arguments]<#:make-flags>: Add the
symbol '64_' as suffix.

gnu/packages/maths.scm

@@ -4635,7 +4635,10 @@ (define-public openblas-ilp64
     (arguments
      (substitute-keyword-arguments (package-arguments openblas)
        ((#:make-flags flags #~'())
-        #~(append (list "INTERFACE64=1" "LIBNAMESUFFIX=ilp64")
+        ;; These should be '64' but julia hardcodes '64_'.
+        #~(append (list "INTERFACE64=1"
+                        "SYMBOLSUFFIX=64_"
+                        "LIBPREFIX=libopenblas64_")
                  #$flags))))
     (synopsis "Optimized BLAS library based on GotoBLAS (ILP64 version)")
     (license license:bsd-3)))