julia: start with a single thread for OpenBLAS

Add patch julia-0001-Allow-OpenBLAS-NUM_THREADS-to-be-overwritten.patch
which makes it possible to specify the maximum number of threads to be used
by OpenBLAS on the make command line instead of using the values
computed by the julia build system which depend on the build host.

Set the maxmum number of threads to be used by OpenBLAS to 80.

Add patch julia-0002-Start-up-OpenBLAS-with-1-thread-per-default.patch
which configures OpenBLAS to use only one thread instead of the maximum
possible number from julia startup. To use more threads, julia can be
started with and environment variable OPENBLAS_NUM_THREADS, e.g.

    OPENBLAS_NUM_THREADS=8 julia

As a result, we default to one thread but can scale up to 80.

	buczek@nomatophobie:~$ julia -q
	julia> ccall((:openblas_get_num_threads64_, Base.libblas_name), Cint, ())
	1
	julia> BLAS.set_num_threads(9999)
	julia> ccall((:openblas_get_num_threads64_, Base.libblas_name), Cint, ())
	80
	julia>
	buczek@nomatophobie:~$ OPENBLAS_NUM_THREADS=8 julia -q
	julia> ccall((:openblas_get_num_threads64_, Base.libblas_name), Cint, ())
	8
	julia>

julia.be0

@@ -15,7 +15,8 @@ SRCURL[0]="https://github.com/JuliaLang/julia/releases/download/v${PKGVERSION}/j
 ## Add URLs/pathes to patch files to the PATCHURL array.
 ## The sources will be patched in the order of the array.
 
-# PATCHURL+=()
+PATCHURL+=(/src/mariux/patches/julia-0001-Allow-OpenBLAS-NUM_THREADS-to-be-overwritten.patch)
+PATCHURL+=(/src/mariux/patches/julia-0002-Start-up-OpenBLAS-with-1-thread-per-default.patch)
 
 ###############################################################################
 ## Add filename patterns to the EXCLUDE array of files that should not
@@ -63,7 +64,8 @@ mee_build() {
     # own purpose.
     # julias Makefile wants prefix lower case
     #
-    start_cmd make ${BEE_MAKEFLAGS} prefix="${PREFIX}" MARCH=x86-64
+    start_cmd make ${BEE_MAKEFLAGS} prefix="${PREFIX}" MARCH=x86-64 \
+      OPENBLAS_NUM_THREADS=80
 }
 
 mee_install() {