Use toolchain's struct stat if available

[facchinm]

Summary of changes

Include <sys/stat.h> (if it's available ) to provide struct stat.
Fixes arduino/ArduinoCore-nRF528x-mbedos#49
The patch should be as safe as possible, since __has_include is guarded itself.

Impact of changes

Adds sizeof(dev_t) on every instance since GCC defines it as

struct  stat
{
  dev_t         st_dev;
  ino_t         st_ino;
  mode_t        st_mode;
  nlink_t       st_nlink;
  uid_t         st_uid;
  gid_t         st_gid;
  dev_t         st_rdev;
  off_t         st_size;
#if defined(__rtems__)
  struct timespec st_atim;
  struct timespec st_mtim;
  struct timespec st_ctim;
  blksize_t     st_blksize;
  blkcnt_t      st_blocks;
#else
  /* SysV/sco doesn't have the rest... But Solaris, eabi does.  */
#if defined(__svr4__) && !defined(__PPC__) && !defined(__sun__)
  time_t        st_atime;
  time_t        st_mtime;
  time_t        st_ctime;
#else
  time_t        st_atime;
  long          st_spare1;
  time_t        st_mtime;
  long          st_spare2;
  time_t        st_ctime;
  long          st_spare3;
  long          st_blksize;
  long          st_blocks;
  long  st_spare4[2];
#endif
#endif
};

and dev_t st_rdev; is not part of mbed's struct.

Migration actions required

Documentation

None

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Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

Only tested on GCC_ARM, hope the CI helps with the other targets.

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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[ciarmcom]

@facchinm, thank you for your changes.
@ARMmbed/mbed-os-core @ARMmbed/mbed-os-maintainers please review.

[kjbracey]

Seems reasonable to me. I wasn't aware GCC supported __has_include in C++14 mode. Other compilers might not, but I guess as you're aiming for GCC it's fine.

[adbridge]

@kjbracey-arm if you have looked at this and are happy could you approve please ?

[adbridge]

CI started

[mbed-ci]

Test run: FAILED

Summary: 1 of 7 test jobs failed
Build number : 1
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_greentea-test

[0xc0170]

tests restarted

[mbed-ci]

Test run: SUCCESS

Summary: 7 of 7 test jobs passed
Build number : 2
Build artifacts