build: make check: disable sim_test when built with --disable-pcsc

Numerous issues caused sim_test to be attempted even though libosmosim was not
built:

In configure.ac, the ENABLE_PCSC variable lacked an AC_SUBST() to be exported.

Furthermore in configure.ac, no value 'yes'/'no' was assigned to the
ENABLE_PCSC variable, only to the enable_pcsc value.

In testsuite.at, encapsulating the sim_test in 'if ENABLE_PCSC' seems to have
no effect, regardless (not even when using a variable that should be defined
accurately).

So fix with these steps, similarly to how we do it in openbsc:

In AC_ARG_ENABLE, directly use 'ENABLE_PCSC' to assign 'yes'/'no'.
Export the same using AC_SUBST().
Add tests/atlocal.in to translate ENABLE_PCSC to enable_sim_test (also add
atlocal to AC_OUTPUT and distclean).
Use enable_sim_test in testuite.at, as seen in openbsc: use AT_CHECK() to
indicate skipping the test if enable_sim_test isn't 'yes'.

Change-Id: I9e8740c7d2dfbd272e22fee85972ef3fda7184a8
diff --git a/configure.ac b/configure.ac
index ea68839..ec03c26 100644
--- a/configure.ac
+++ b/configure.ac
@@ -104,15 +104,16 @@
 
 AC_ARG_ENABLE([pcsc], [AS_HELP_STRING([--disable-pcsc], [Build without PC/SC support])],
     [
-        enable_pcsc=$enableval
+        ENABLE_PCSC=$enableval
     ],
     [
-        enable_pcsc="yes"
+        ENABLE_PCSC="yes"
     ])
-AS_IF([test "x$enable_pcsc" = "xyes"], [
+AS_IF([test "x$ENABLE_PCSC" = "xyes"], [
 	PKG_CHECK_MODULES(PCSC, libpcsclite)
 ])
-AM_CONDITIONAL(ENABLE_PCSC, test "x$enable_pcsc" = "xyes")
+AM_CONDITIONAL(ENABLE_PCSC, test "x$ENABLE_PCSC" = "xyes")
+AC_SUBST(ENABLE_PCSC)
 
 AC_ARG_ENABLE(plugin,
 	[AS_HELP_STRING(
@@ -231,6 +232,7 @@
 	src/gb/Makefile
 	src/ctrl/Makefile
 	tests/Makefile
+	tests/atlocal
 	utils/Makefile
 	Doxyfile.core
 	Doxyfile.gsm