[clang] [flang][driver] Mark -fcommon and -mtune as visible in Flang (PR #68657)

[Andrzej Warzyński via cfe-commits]

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@@ -10,6 +10,9 @@
 ! Make sure that `-L' is "visible" to Flang's driver
 ! RUN: %flang -L/ -### %s
 
+! Make sure that `-fcommon' is "visible" to Flang's driver
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banach-space wrote:

This is not clear because I didn't leave any comment in this file (mea culpa, sorry), but the other flags tested here are purely driver flags (i.e. there's is nothing for Flang to do here). However, IIUC, `-fcommon` will affect code-generation and that's what we should be testing here instead,

https://github.com/llvm/llvm-project/pull/68657