[clang] [flang] [flang][Driver] Better error message when multiple actions are specified (PR #165575)

[David Spickett via cfe-commits]

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@@ -312,6 +312,8 @@ def warn_drv_yc_multiple_inputs_clang_cl : Warning<
 def warn_drv_potentially_misspelled_joined_argument : Warning<
   "joined argument treated as '%0'; did you mean '%1'?">, InGroup<UnknownArgument>;
 
+def err_drv_too_many_actions: Error<
+    "only one action option is allowed. Got '%0'">;
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DavidSpickett wrote:

You strip a set of `''` later, could you remove them from here instead, or are they part of the substitution syntax?

https://github.com/llvm/llvm-project/pull/165575