Correctly set the linker search path for libm and libc.

  - ndk/r10 is removed, we need to use SOONG ndk stubs instead.
  - Use MIN_SUPPORTED_SDK_VERSION instead of hard coded version 9 for
    32 bit compilation.

Bug: 38342163
Test: mm
Test: make -j40 FORCE_BUILD_RS_COMPAT=true RSTest_Compat
Change-Id: I9549446cb7f8faee8842b06f096d035535dc7f3d