preinst-swig script support for native windows paths

- SWIG_LIB support for testing on Windows
- Only in-source builds for now

configure.ac

@@ -2656,6 +2656,7 @@ AC_SUBST(SKIP_ANDROID)
 # Miscellaneous
 #----------------------------------------------------------------
 
+ABS_SRCDIR=`(cd ${srcdir} && pwd)`
 
 # Root directory
 # Translate path for native Windows compilers for use with 'make check'
@@ -2689,6 +2690,14 @@ case $build in
 esac
 AC_DEFINE_UNQUOTED(SWIG_LIB_WIN_UNIX, ["$SWIG_LIB_WIN_UNIX"], [Directory for SWIG system-independent libraries (Unix install on native Windows)])
 
+# For testing - Windows builds of SWIG do not need SWIG_LIB set
+AC_EGREP_CPP([yes],
+[#ifdef _WIN32
+  yes
+#endif
+], [SWIG_LIB_PREINST=], [SWIG_LIB_PREINST=$ABS_SRCDIR/Lib])
+AC_SUBST(SWIG_LIB_PREINST)
+
 AC_CONFIG_FILES([
     Makefile
     swig.spec

preinst-swig.in

@@ -1,7 +1,5 @@
 #!/bin/sh
 builddir=`dirname $0`
-srcdir=`cd "$builddir" && cd '@srcdir@' && pwd`
-SWIG_LIB=$srcdir/Lib
-#SWIG_LIB=`cygpath -w $srcdir/Lib` # For native Windows version of SWIG
+SWIG_LIB=@SWIG_LIB_PREINST@
 export SWIG_LIB
 exec "$builddir/swig" "$@"