Changes

[sanitizer] Define SANITIZER_GLIBC to refine SANITIZER_LINUX feature detection and support musl

Several `#if SANITIZER_LINUX && !SANITIZER_ANDROID` guards are replaced
with the more appropriate `#if SANITIZER_GLIBC` (the headers are glibc
extensions, not specific to Linux (i.e. if we ever support GNU/kFreeBSD
or Hurd, the guards may automatically work)).

Several `#if SANITIZER_LINUX && !SANITIZER_ANDROID` guards are refined
with `#if SANITIZER_GLIBC` (the definitions are available on Linux glibc,
but may not be available on other libc (e.g. musl) implementations).

This patch makes `ninja asan cfi msan stats tsan ubsan xray` build on a musl based Linux distribution (apk install musl-libintl)
Notes about disabled interceptors for musl:

* `SANITIZER_INTERCEPT_GLOB`: musl does not implement `GLOB_ALTDIRFUNC` (GNU extension)
* Some ioctl structs and functions operating on them.
* `SANITIZER_INTERCEPT___PRINTF_CHK`: `_FORTIFY_SOURCE` functions are GNU extension
* `SANITIZER_INTERCEPT___STRNDUP`: `dlsym(RTLD_NEXT, "__strndup")` errors so a diagnostic is formed. The diagnostic uses `write` which hasn't been intercepted => SIGSEGV
* `SANITIZER_INTERCEPT_*64`: the `_LARGEFILE64_SOURCE` functions are glibc specific. musl does something like `#define pread64 pread`
* Disabled `msg_iovlen msg_controllen cmsg_len` checks: musl is conforming while many implementations (Linux/FreeBSD/NetBSD/Solaris) are non-conforming. Since we pick the glibc definition, exclude the checks for musl (incompatible sizes but compatible offsets)

Pass through LIBCXX_HAS_MUSL_LIBC to make check-msan/check-tsan able to build libc++ (https://bugs.llvm.org/show_bug.cgi?id=48618).

Many sanitizer features are available now.

```
% ninja check-asan
(known issues:
* ASAN_OPTIONS=fast_unwind_on_malloc=0 odr-violations hangs
)
...
Testing Time: 53.69s
  Unsupported      : 185
  Passed           : 512
  Expectedly Failed:   1
  Failed           :  12

% ninja check-ubsan check-ubsan-minimal check-memprof # all passed

% ninja check-cfi
( all cross-dso/)
...
Testing Time: 8.68s
  Unsupported      : 264
  Passed           :  80
  Expectedly Failed:   8
  Failed           :  32

% ninja check-msan
(Many are due to functions not marked unsupported.)
Testing Time: 23.09s
  Unsupported      :   6
  Passed           : 764
  Expectedly Failed:   2
  Failed           :  58

% ninja check-tsan
Testing Time: 23.21s
  Unsupported      :  86
  Passed           : 295
  Expectedly Failed:   1
  Failed           :  25
```

Used `ASAN_OPTIONS=verbosity=2` to verify no unneeded interceptors.

Partly based on Jari Ronkainen's https://reviews.llvm.org/D63785#1921014

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D93848

[sanitizer] Include fstab.h on glibc/FreeBSD/NetBSD/macOS