Update git submodules

* Update ndk from branch 'ndk-release-r19'
  to 1904f74db06e44e280e4ac977f0e5a212527e3a0
  - Merge changes I77002416,Ibdb2254e,I5cb7b38f into ndk-release-r19
    
    * changes:
      Update changelog to mention fix in r19b.
      Only use -stdlib=libc++ with clang++.
      Now r19b canary.
    
  - Update changelog to mention fix in r19b.
    
    Test: None
    Bug: android/ndk#849
    Change-Id: I770024162863e3a3a5ccebcefdebf8da43b031a4
    
  - Only use -stdlib=libc++ with clang++.
    
    Test: Manual inspection of build flags with `clang -v`
    Bug: android/ndk#849
    Change-Id: Ibdb2254ee9e91f94c59c8c9c794b19ae617ef6d2
    (cherry picked from commit dc2cc5f94756878c2ae214f47988bed1302aef5b)
    
  - Now r19b canary.
    
    Test: ./checkbuild.py
    Bug: None
    Change-Id: I5cb7b38f4bff55f1ebe50d5f03aa2481b3fe85c2