[clang][test] Rewrote test using command substitution to work with li…

…t internal shell syntax (llvm#105902)

This patch rewrites a test that uses command substitution `$()` and the
`stat` command, which are not supported by lit's internal shell. Instead
of using this syntax to perform the file size comparison done in this
test, a Python script is used instead to perform the same operation.

Fixes llvm#102384.

clang/test/Modules/compare-file-size.py

@@ -0,0 +1,20 @@
+# This program takes in two file path arguments in the form 'compare-file-size.py file1 file2'
+# Returns true if the file size of the file1 is smaller than the file size of file2
+
+import argparse
+import os
+
+
+def main():
+    parser = argparse.ArgumentParser()
+
+    parser.add_argument("file1", type=str)
+    parser.add_argument("file2", type=str)
+
+    args = parser.parse_args()
+
+    return os.path.getsize(args.file1) < os.path.getsize(args.file2)
+
+
+if __name__ == "__main__":
+    main()

clang/test/Modules/reduced-bmi-size.cppm

@@ -10,7 +10,6 @@
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface %s -o %t/a.pcm
 // RUN: %clang_cc1 -std=c++20 -emit-reduced-module-interface %s -o %t/a.reduced.pcm
 //
-// %s implies the current source file. So we can't use it directly.
-// RUN: [ $(stat -c%\s "%t/a.pcm") -le $(stat -c%\s "%t/a.reduced.pcm") ]
+// RUN: %python %S/compare-file-size.py %t/a.pcm %t/a.reduced.pcm
 
 export module a;