build.gradle: comment

Author: stephengold

build.gradle

@@ -69,7 +69,7 @@ model {
     toolChains { // prioritize among the native toolchains
         visualCpp(VisualCpp) // used when compiling on Windows
         //clang(Clang) // to prefer Clang over Gcc on Linux
-        gcc(Gcc) // used when compiling on Linux
+        gcc(Gcc) // default when compiling on Linux
         clang(Clang) // used when compiling on macOS
 
         gcc10Arm(Gcc) { // used at Travis CI and GitHub Actions