Edit jamfile

Author: mborland

test/Jamfile

@@ -30,7 +30,8 @@ project : requirements
   <toolset>gcc:<cxxflags>-Wfloat-equal
   <toolset>gcc:<cxxflags>-Wshadow
   # https://github.com/cppalliance/decimal/issues/1291
-  <toolset>gcc:<cxxflags>-Wextra-semi
+  # GCC-7 does not support extra-semi, just pick one to try
+  <toolset>gcc-13:<cxxflags>-Wextra-semi
   <toolset>gcc:<cxxflags>-Wuseless-cast
   # <toolset>gcc:<cxxflags>-Wpadded