[libc] Fix warnings on release build.

[PaulkaToast]

Summary

These warnings were present when building llvm-libc in release mode.

workspace/llvm-project/libc/utils/benchmarks/LibcMemoryBenchmarkTest.cpp:50:34: warning: 'None' is deprecated: Use Align() or Align(1) instead [-Wdeprecated-declarations]
  Conf.AddressAlignment = Align::None();

workspace/llvm-project/libc/utils/testutils/FDReaderUnix.cpp:19:7: warning: unused variable 'err' [-Wunused-variable]
  int err = ::pipe(pipefd);

For test-utils it seems in general we should use report_fatal_error instead of asserts as these are turned off when building in release mode.
https://llvm.org/docs/CodingStandards.html#assert-liberally

[sivachandra]

LGTM, but wait for @abrachet.

[abrachet]

libc/utils/benchmarks/LibcMemoryBenchmarkTest.cpp

49–50

AddressAlignment is already defaulted in StudyConfiguration's default ctor so we don't need this line.

libc/utils/testutils/FDReaderUnix.cpp

18–20

Maybe if (::pipe(pipefd))?

libc/utils/benchmarks/LibcMemoryBenchmarkTest.cpp

TEST(OffsetDistribution, AlignToBegin) {
   OffsetDistribution OD(Conf);
   std::default_random_engine Gen;
   for (size_t I = 0; I <= 10; ++I)
     EXPECT_EQ(OD(Gen), 0U);
 }
 
 TEST(OffsetDistribution, NoAlignment) {
   StudyConfiguration Conf;
   Conf.BufferSize = 8192;
-  Conf.AddressAlignment = Align::None();
   Conf.Size.To = 1;
 
   OffsetDistribution OD(Conf);
   std::default_random_engine Gen;
   for (size_t I = 0; I <= 10; ++I)
     EXPECT_THAT(OD(Gen), AllOf(Ge(0U), Lt(8192U)));
 }
 
 MATCHER_P(IsDivisibleBy, n, "") {

libc/utils/testutils/FDReaderUnix.cpp

 #include "llvm/Support/MemoryBuffer.h"
 #include <cassert>
 #include <cstring>
 #include <unistd.h>
 
 namespace __llvm_libc {
 namespace testutils {
 
 FDReader::FDReader() {
-  int err = ::pipe(pipefd);
-  assert(!err && "pipe(2) failed");
+  if (::pipe(pipefd))
+    llvm::report_fatal_error("pipe(2) failed");
 }
 
 FDReader::~FDReader() {
   ::close(pipefd[0]);
   ::close(pipefd[1]);
 }
 
 bool FDReader::matchWritten(const char *str) {