Add util.sh shell library

A shell utilities function library starting with a first utility
function for getting the number of online CPUs.

Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>

.shellcheckrc

@@ -0,0 +1,2 @@
+external-sources=true
+source-path=source/tools

source/tools/utils.sh

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+#!/bin/sh
+
+# Collection of sh utilities
+
+# Return number of online cpu or 1 if it can't be determined.
+utils_num_online_cpu()
+{
+	getconf _NPROCESSORS_ONLN 2>/dev/null && return
+	getconf NPROCESSORS_ONLN 2>/dev/null && return
+	nproc 2>/dev/null && return
+	sysctl -m hw.nproc 2>/dev/null && return
+	echo 1
+}