[Ada] Fix typo in error message

An error message mentions "gnamake", where it meant to mention
"gnatmake".

2019-09-18  Tom Tromey  <tromey@adacore.com>

gcc/ada/

	* make.adb (Initialize): Fix typo.

From-SVN: r275844

gcc/ada/ChangeLog

+2019-09-18  Tom Tromey  <tromey@adacore.com>
+
+	* make.adb (Initialize): Fix typo.
+
 2019-09-18  Olivier Hainque  <hainque@adacore.com>
 
 	* libgnat/s-win32.ads (DWORD_PTR): New type, pointer size

gcc/ada/make.adb

@@ -3789,7 +3789,7 @@ package body Make is
 
                if Gprbuild = null then
                   Fail_Program
-                    ("project files are no longer supported by gnamake;" &
+                    ("project files are no longer supported by gnatmake;" &
                      " use gprbuild instead");
                end if;