On z/OS, umask() returns an int because mode_t is type int, however it is being compared to an unsigned int. This patch fixes the following warning we see when compiling Path.cpp.
```
comparison of integers of different signs: 'const int' and 'const unsigned int'
```
Reviewed By: muiez
Differential Revision: https://reviews.llvm.org/D102326
unsigned CurrentMask = fs::getUmask();
EXPECT_EQ(CurrentMask, 0022U)
<< "getUmask() didn't return previously set umask()";
- EXPECT_EQ(::umask(OldMask), 0022U) << "getUmask() may have changed umask()";
+ EXPECT_EQ(::umask(OldMask), mode_t(0022U))
+ << "getUmask() may have changed umask()";
#endif
}