Add Makefile for Apple ARM64 machines

Makefile

@@ -26,4 +26,4 @@ clean:
 
 install: all
 	mkdir -p ${PLUGINDIR}/qwrap${VERSION} && \
-		rsync -av qwrap.so pkgIndex.tcl ${PLUGINDIR}/qwrap${VERSION}/. 
+		rsync -av qwrap.so pkgIndex.tcl ${PLUGINDIR}/qwrap${VERSION}/.

Makefile.OSX_ARM64

@@ -0,0 +1,32 @@
+
+VERSION=1.6
+VMDDIR="/Applications/VMD\ 1.9.4a55-arm64-Rev11.app/Contents/vmd"
+TCLINC=-I/usr/include/tcl8.6
+#TCLLIB=-L/usr/lib64 -ltclstub8.6
+PLUGINDIR=${VMDDIR}/plugins/MACOSXAMD64/tcl
+FRAMEWORK=-F ${VMDDIR}/../Frameworks -framework Tcl
+
+# Tested with g++ and clang++
+CXX=g++
+#CXX=clang++
+CPPFLAGS=-fpic -O3 -Wall ${TCLINC} -DVERSION=\"${VERSION}\"
+
+all: qwrap.so.${VERSION} pkgIndex.tcl
+
+qwrap.so.${VERSION}: qwrap.o
+	$(CXX) -dynamiclib -DUSE_TCL_STUBS $< ${FRAMEWORK} -o $@
+	ln -s -f qwrap.so.${VERSION} qwrap.so
+
+qwrap.tar.gz: qwrap.cpp Makefile pkgIndex.tcl
+	tar czf qwrap${VERSION}.tar.gz qwrap.cpp Makefile pkgIndex.tcl
+
+pkgIndex.tcl: qwrap.so
+	tclsh mkindex.tcl
+
+clean:
+	rm -f *.o *.so
+
+install: all
+	mkdir -p ${PLUGINDIR}/qwrap${VERSION} && \
+		rsync -av qwrap.so pkgIndex.tcl ${PLUGINDIR}/qwrap${VERSION}/.
+

README.md

@@ -29,6 +29,12 @@ First make sure Tcl development packages are installed (tcl-dev or tcl-devel).
 tar xf qwrap.tar.gz (in own directory) 
 make
 ```
+
+For Macs with ARM64 processors (M1, M2, M3 etc.), try adapting the paths in `Makefile.OSX_ARM64` and running:
+```
+make -f Makefile.OSX_ARM64
+```
+
 Optionally, install as a VMD plugin:
 ```
 # update the PLUGINDIR variable in Makefile