wscript: try to fix install on windows

scripts/gha/build_win32.sh

@@ -11,9 +11,9 @@ fi
 
 # NOTE: to build with other version use --msvc_version during configuration
 # NOTE: sometimes you may need to add WinSDK to %PATH%
-./waf.bat configure -s "SDL2_VC" -T "debug" --enable-utils $AMD64 || die
+./waf.bat configure -s "SDL2_VC" -T "debug" --enable-utils --prefix=`pwd` $AMD64 || die
 ./waf.bat build -v || die
-./waf.bat install --prefix=`pwd` || die
+./waf.bat install || die
 
 if [ "$ARCH" = "i386" ]; then
 	cp SDL2_VC/lib/x86/SDL2.dll . # Install SDL2

wscript

@@ -295,8 +295,10 @@ def configure(conf):
 		conf.env.LIBDIR = conf.env.BINDIR = '${PREFIX}/lib/xash3d'
 		conf.env.SHAREDIR = '${PREFIX}/share/xash3d'
 	else:
+		if sys.platform != 'win32':
 			conf.env.PREFIX = '/'
-		conf.env.SHAREDIR = conf.env.LIBDIR = conf.env.BINDIR = '/'
+
+		conf.env.SHAREDIR = conf.env.LIBDIR = conf.env.BINDIR = conf.env.PREFIX
 
 	conf.define('XASH_BUILD_COMMIT', conf.env.GIT_VERSION if conf.env.GIT_VERSION else 'notset')
 	conf.define('XASH_LOW_MEMORY', conf.options.LOW_MEMORY)