tests: use -no-install libtool flag to avoid ./lt-* scripts

This option should be used for any executables which are used only
for testing, or for generating other files and are consequently never
installed.  By specifying this option, we are telling Libtool that
the executable it links will only ever be executed from where it is
built in the build tree.  Libtool is usually able to considerably
speed up the link process for such executables.

Change-Id: I4bc03bdc1f2de2574558e2ad753e116486993a7f

tests/mgcp/Makefile.am

@@ -18,6 +18,7 @@ AM_CFLAGS = \
 
 AM_LDFLAGS = \
 	$(COVERAGE_LDFLAGS) \
+	-no-install \
 	$(NULL)
 
 EXTRA_DIST = \

tests/mgcp_client/Makefile.am

@@ -15,6 +15,7 @@ AM_CFLAGS = \
 
 AM_LDFLAGS = \
 	$(COVERAGE_LDFLAGS) \
+	-no-install \
 	$(NULL)
 
 EXTRA_DIST = \