Use a PACKAGE_MSI environment variable to control whether or not the script

continues execution.  If this is not set to 1, the script will exit without
attempting to create the MSI.

browser/installer/windows/msi/make-msi.pl

@@ -11,6 +11,15 @@ if (!$win32) {
     die "ERROR: MSI installers can currently only be made on Windows platforms\n";
 }
 
+#--------------------------------------------------------------------------
+# If $ENV{PACKAGE_MSI} is not true, exit.
+#--------------------------------------------------------------------------
+
+if (!exists($ENV{PACKAGE_MSI}) or !defined($ENV{PACKAGE_MSI}) or ($ENV{PACKAGE_MSI} ne 1) ) {
+    printf("make-msi.pl: PACKAGE_MSI environment variable is not true.. exiting.\n");
+    exit;
+}
+
 #--------------------------------------------------------------------------
 # Find the MakeMSI mm.cmd program.
 #--------------------------------------------------------------------------

toolkit/mozapps/installer/windows/msi/make-msi.pl

@@ -11,6 +11,15 @@ if (!$win32) {
     die "ERROR: MSI installers can currently only be made on Windows platforms\n";
 }
 
+#--------------------------------------------------------------------------
+# If $ENV{PACKAGE_MSI} is not true, exit.
+#--------------------------------------------------------------------------
+
+if (!exists($ENV{PACKAGE_MSI}) or !defined($ENV{PACKAGE_MSI}) or ($ENV{PACKAGE_MSI} ne 1) ) {
+    printf("make-msi.pl: PACKAGE_MSI environment variable is not true.. exiting.\n");
+    exit;
+}
+
 #--------------------------------------------------------------------------
 # Find the MakeMSI mm.cmd program.
 #--------------------------------------------------------------------------