Be able to switch-off ASAN builds of our binaries.

Inroduce a way to not take a 2x performance hit when testing. It
is of importance if we run with hundreds of BTSes and 10k+ subscribers.
In the absence of using getops or shflags use an environment for it.

Change-Id: I540ba1c35e8fb72abcee0d86e0bdc1136b47345c
diff --git a/contrib/jenkins-build-common.sh b/contrib/jenkins-build-common.sh
index ceee5c0..17ab7df 100644
--- a/contrib/jenkins-build-common.sh
+++ b/contrib/jenkins-build-common.sh
@@ -49,6 +49,10 @@
 # osmo-bts within the sysmoBTS SDK
 prefix_real="${prefix_real-"$prefix"}"
 
+# Flag to be used to enable ASAN in builds. Defaults to enable ASAN builds and
+# it can be disabled by passing SANITIZE_FLAGS="" to the build.
+SANITIZE_FLAGS="${SANITIZE_FLAGS---enable-sanitize}"
+
 export PKG_CONFIG_PATH="$prefix_real/lib/pkgconfig:$PKG_CONFIG_PATH"
 export LD_LIBRARY_PATH="$prefix_real/lib:$LD_LIBRARY_PATH"