NFC casing in buildconfig/global.txt

Author: pcanal

.github/workflows/root-ci-config/buildconfig/global.txt

@@ -46,7 +46,7 @@ davix=ON
 dcache=OFF
 dev=OFF
 distcc=OFF
-fail-on-missing=On
+fail-on-missing=ON
 fcgi=OFF
 fftw3=ON
 fitsio=ON