Update git submodules

* Update platform/ndk from branch 'master'
  to 27f979a34b6ca75c70a659fafa58f7ed4d3bfabe
  - Merge "Build libm with _GNU_SOURCE."
  - Build libm with _GNU_SOURCE.
    
    To avoid:
    
      ndk/bionic/libm/upstream-freebsd/lib/msun/src/k_exp.c:108:2:
        error: implicit declaration of function 'sincos' is invalid in C99
            sincos(y, &s, &c);
            ^
      1 error generated.
    
    Test: treehugger
    Change-Id: I1c3b9f7583a92aec4809f073806f19516c66054d
    
1 file changed