[llvm-lipo] Update llvm-lipo docs for -archs flag

[anushabasana]

Summary

The information for -archs flag is added to llvm-lipo.rst.

Test Plan:

[alexander-shaposhnikov]

I've added one inline comment, other than that - LGTM, I'd wait for @mtrent as well )

llvm/docs/CommandGuide/llvm-lipo.rst

32 ↗

(On Diff #203909)

maybe add a bit more details similar to what the man page says:
"Each architecture name is a single word, making this option
suitable for shell scripting. Unknown architectures will be represented by "unknown" along with the numeric CPU type and CPU subtype values as a single word.", though personally I don't insist.

[anushabasana]

Added more detail

[mtrent]

approving this revision in light of my notes inline. I still believe this command guide is going to need an editorial pass once all of the options are in. my main concern for the moment is that the information is accurate and complete.

llvm/docs/CommandGuide/llvm-lipo.rst

34 ↗

(On Diff #203925)

Hmmmm .... I'm going to provide this feedback so I'm not repeating the contents of the Apple man page, which may be under copyright.

The main idea here is:

1. archs takes a single input file
2. each arch is printed by itself separated by whitespace. (It so happens that arches are also single words, but that's kind of obvious.)

These two facts taken together means that -archs is well suited for shell scripting, where can do something like "foreach i (llvm-lipo -archs <file>)"

My problem with the content here is that " Print architectures as a single word so -archs is suitable for shell scripting." is clumsy and doesn't quite make sense. Easiest edit might just be to say:

"Take a single input file and display the architectures present in the file. Each architecture is separated only by whitespace. Unknown architectures are displayed as unknown(CPUtype,CPUsubtype)."

and let the chips fall where they may.

[anushabasana]

Clarified description.

[smeenai]

I'll go ahead and commit this since all comments have been addressed.

llvm/trunk/docs/CommandGuide/llvm-lipo.rst

.. option:: -version
 
   Display the version of this program. 
 
 .. option:: -verify_arch  <architecture 1> [<architecture 2> ...]
 
   Take a single input file and verify the specified architectures are present in the file. 
   If so then exit with a status of 0 else exit with a status of 1.
 
+.. option:: -archs
+
+  Take a single input file and display the architectures present in the file.
+  Each architecture is separated by a single whitespace.
+  Unknown architectures are displayed as unknown(CPUtype,CPUsubtype).
+
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