Slight simplification of test-suite build for new out-of-source changes

Provide default SRCDIR and SCRIPTDIR variables in common.mk and override
only where needed.

Examples/test-suite/java/Makefile.in

@@ -6,17 +6,11 @@ LANGUAGE     = java
 JAVA         = @JAVA@
 JAVAC        = @JAVAC@
 JAVAFLAGS    = -Xcheck:jni
-SCRIPTDIR    = $(srcdir)
 SCRIPTSUFFIX = _runme.java
 
 srcdir       = @srcdir@
 top_srcdir   = ../@top_srcdir@
 top_builddir = ../@top_builddir@
-ifeq (.,$(srcdir))
-SRCDIR = ../
-else
-SRCDIR = ../$(srcdir)/
-endif
 
 C_TEST_CASES = \
 	java_lib_arrays \
@@ -49,6 +43,7 @@ CPP_TEST_CASES = \
 include $(srcdir)/../common.mk
 
 # Overridden variables here
+SRCDIR       = ../$(srcdir)/
 JAVA_PACKAGE = $*
 JAVA_PACKAGEOPT = -package $(JAVA_PACKAGE)
 SWIGOPT += $(JAVA_PACKAGEOPT)