[NFC][AIX]Disable precompiled module file tests on AIX

[stevewan]

Summary

The PCH reader looks for __clangast section in the precompiled module file, which is not present in the file on AIX, and we don't support writing this custom section in XCOFF yet.

[daltenty]

LGTM, with minor nit.

clang/test/ClangScanDeps/modules-pch-common-submodule.c

1

Let's add a comment, to let folks know what's going on with these. Something like:

// Unsupported on AIX because we don't support the requisite __clangast section in XCOFF yet.

[stevewan]

Explain the rationale

clang/test/ClangScanDeps/modules-pch-common-submodule.c

+// UNSUPPORTED: aix
+
 // Check that when depending on a precompiled module, we depend on the
 // **top-level** module. Submodules don't have some information present (for
 // example the path to the modulemap file) and depending on them might cause
 // problems in the dependency scanner (e.g. generating empty `-fmodule-map-file=`
 // arguments).
 
 // RUN: rm -rf %t && mkdir %t
 // RUN: cp %S/Inputs/modules-pch-common-submodule/* %t

clang/test/ClangScanDeps/modules-pch-common-via-submodule.c

+// UNSUPPORTED: aix
+
 // Check that we discover dependency on a precompiled module (and generate the
 // appropriate `-fmodule-file=` argument) when it's imported by a **submodule**
 // instead of a top-level module.
 
 // RUN: rm -rf %t && mkdir %t
 // RUN: cp %S/Inputs/modules-pch-common-via-submodule/* %t
 
 // Scan dependencies of the PCH:

clang/test/ClangScanDeps/modules-pch.c

+// UNSUPPORTED: aix
+
 // RUN: rm -rf %t && mkdir %t
 // RUN: cp %S/Inputs/modules-pch/* %t
 
 // Scan dependencies of the PCH:
 //
 // RUN: sed "s|DIR|%/t|g" %S/Inputs/modules-pch/cdb_pch.json > %t/cdb.json
 // RUN: echo -%t > %t/result_pch.json
 // RUN: clang-scan-deps -compilation-database %t/cdb.json -format experimental-full \

clang/test/PCH/debug-info-pch-path.c

+// UNSUPPORTED: aix
+
 // RUN: rm -rf %t
 // RUN: mkdir %t
 // RUN: cd %t
 //
 // ---------------------------------------------------------------------
 // Relative PCH, same directory.
 // ---------------------------------------------------------------------
 //