Update runtime files
diff --git a/src/INSTALLmac.txt b/src/INSTALLmac.txt
index 9980d25..2e8a656 100644
--- a/src/INSTALLmac.txt
+++ b/src/INSTALLmac.txt
@@ -59,6 +59,8 @@
Build and install the GUI version with X-Windows
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+NOTE: this probably no longer works, since Athena support has been removed.
+
First, install XQuartz, which you can download from https://www.xquartz.org.
To tell configure to use a GUI you can edit the Makefile and uncomment these