OpenBLAS: give instructions for Broadwell CPU

component/openblas/buildout.cfg

@@ -4,6 +4,11 @@ parts =
 
 [openblas]
 recipe = slapos.recipe.cmmi
+# OpenBLAS 0.2.13 and 0.2.14 does not build on Broadwell
+# CPU (Detecting CPU failed). But version 0.2.15 (which
+# does not exist yet) will fix the issue. Until then you
+# can add in options :
+# TARGET=HASWELL
 url = http://github.com/xianyi/OpenBLAS/tarball/v0.2.13
 md5sum = 74adf4c0d0d82bff4774be5bf2134183
 configure-command = true