fsx,fsxc: deprecate --check/-k flag

In the cases where launcher.sh is used (instead of fsx.fsproj),
the -k flag was being passed to fsxc successfully, but then the
script would be run. As fixing this would be a bit messy (would
need lots of bash hacks in the launcher), let's rather
deprecate it; and if someone needs to only compile the script,
they can call fsxc directly (which is what we advice in the
deprecation error message).

Fixes #37

fsx/Program.fs

@@ -135,6 +135,14 @@ let InjectBinSubfolderInPath(userScriptPath: string) =
 
 let fsxcArgs, maybeUserScriptPath, userArgs = SplitArgsIntoFsxcArgsAndUserArgs()
 
+if fsxcArgs.Any(fun arg -> arg = "--check" || arg = "-k") then
+    Console.Error.WriteLine(
+        "The flag --check/-k is DEPRECATED. "
+        + FSX.Compiler.Program.CheckFlagDeprecationMessage
+    )
+
+    Environment.Exit 1
+
 let fsxcMainArguments =
     match maybeUserScriptPath with
     | Some userScriptPath ->

fsxc/Fsxc.fs

@@ -48,6 +48,8 @@ type ProgramInvocationType =
 exception NoScriptProvided
 
 module Program =
+    let CheckFlagDeprecationMessage =
+        "If you need to only compile (without running), use 'fsxc' instead of 'fsx'"
 
 #if LEGACY_FRAMEWORK
     let private nugetExeTmpLocation: Lazy<FileInfo> =
@@ -94,8 +96,14 @@ module Program =
 
         Console.WriteLine "  -h, --help      Show this help"
 
-        Console.WriteLine
-            "  -k, --check     Only check if it compiles, removing generated binaries"
+        match invocationType with
+        | FsxcPureInvocation ->
+            Console.WriteLine
+                "  -k, --check     Only check if it compiles, removing generated binaries"
+        | FsxLauncherScript ->
+            Console.WriteLine(
+                "  -k, --check     DEPRECATED: " + CheckFlagDeprecationMessage
+            )
 
         Console.WriteLine
             "  -v, --verbose   Verbose mode, ideal for debugging purposes"