Document ASLR for Precompiled Headers.

	PR c++/92717
	* doc/invoke.texi: Document that one should
	not combine ASLR and -fpch.

gcc/ChangeLog

+2020-02-05  Martin Liska  <mliska@suse.cz>
+
+	PR c++/92717
+	* doc/invoke.texi: Document that one should
+	not combine ASLR and -fpch.
+
 2020-02-04  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/93538

gcc/doc/invoke.texi

@@ -31106,6 +31106,10 @@ precompiled header.  The following are known to be safe:
 -fsched-verbose=@var{number}  -fschedule-insns  -fvisibility= @gol
 -pedantic-errors}
 
+@item Address space layout randomization (ASLR) can lead to not binary identical
+PCH files.  If you rely on stable PCH file contents disable ASLR when generating
+PCH files.
+
 @end itemize
 
 For all of these except the last, the compiler automatically