[scudo/standalone] Fix undefined behavior in checksum test

[mcgrathr]

Summary

1U has type unsigned int, and << of 32 or more is undefined behavior.
Use the proper type in the lhs of the shift.

[mcgrathr]

formatting

compiler-rt/lib/scudo/standalone/tests/checksum_test.cpp

template <ComputeChecksum F> void verifyChecksumFunctionBitFlip() {
   scudo::uptr Array[sizeof(scudo::u64) / sizeof(scudo::uptr)];
   const scudo::uptr ArraySize = ARRAY_SIZE(Array);
   memset(Array, 0xaa, sizeof(Array));
   const scudo::u32 Seed = 0x41424343U;
   const scudo::u16 Reference = F(Seed, Array, ArraySize);
   scudo::u8 IdenticalChecksums = 0;
   for (scudo::uptr I = 0; I < ArraySize; I++) {
     for (scudo::uptr J = 0; J < SCUDO_WORDSIZE; J++) {
-      Array[I] ^= 1U << J;
+      Array[I] ^= scudo::uptr{1} << J;
       if (F(Seed, Array, ArraySize) == Reference)
         IdenticalChecksums++;
-      Array[I] ^= 1U << J;
+      Array[I] ^= scudo::uptr{1} << J;
     }
   }
   // Allow for a couple of identical checksums over the whole set of flips.
   EXPECT_LE(IdenticalChecksums, 2);
 }
 
 TEST(ScudoChecksumTest, ChecksumFunctions) {
   verifyChecksumFunctionBitFlip<computeSoftwareChecksum>();
   if (&scudo::computeHardwareCRC32 && scudo::hasHardwareCRC32())
     verifyChecksumFunctionBitFlip<computeHardwareChecksum>();
 }