Update minimum gcc version in installation instructions

Author: wrljet

html/hercinst.html

@@ -124,7 +124,7 @@ <h3>Building from source - Linux and MacOS (High Sierra and newer)</h3>
 <p>
 
 <em><b>Important:</b></em>
-You must use at least version 4.6.2 of the gcc compiler and associated glibc2 library.
+You must use at least version 6.2.0 of the gcc compiler and associated glibc2 library.
 Refer to the <a href="hercfaq.html#3.04">
 Hercules Frequently-Asked Questions</a> page for required
 compiler and other software levels.<br />