build: pkg anti-pattern: use defaults

Use the defaults in the pkg check where the default error message is
sufficient to identify which package is missing.

Change-Id: Ic4e819ff68c05e70b51a8212236def7d33f6d750
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index 6713160..9f2396a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,10 +18,10 @@
 
 # Checks for libraries.
 AC_CHECK_LIB([pthread], [pthread_create])
-PKG_CHECK_MODULES([LIBVNCSERVER], [libvncserver], , AC_MSG_ERROR(["Requires libvncserver package."]))
-PKG_CHECK_MODULES([SDBUSPLUS], [sdbusplus], , AC_MSG_ERROR(["Requires sdbusplus package."]))
-PKG_CHECK_MODULES([PHOSPHOR_LOGGING], [phosphor-logging], , AC_MSG_ERROR(["Requires phosphor-logging package."]))
-PKG_CHECK_MODULES([PHOSPHOR_DBUS_INTERFACES], [phosphor-dbus-interfaces], , AC_MSG_ERROR(["Requires phosphor-dbus-interfaces package."]))
+PKG_CHECK_MODULES([LIBVNCSERVER], [libvncserver])
+PKG_CHECK_MODULES([SDBUSPLUS], [sdbusplus])
+PKG_CHECK_MODULES([PHOSPHOR_LOGGING], [phosphor-logging])
+PKG_CHECK_MODULES([PHOSPHOR_DBUS_INTERFACES], [phosphor-dbus-interfaces])
 
 LT_INIT