[gpgpu] Modify makefile to use Android NDK r16b version
[gpgpu] Modify makefile to use Android NDK r16b version

-Modified config/Linux.mk to support use of clang instead of gcc.
-Some of the gcc optimization flags in cufft.mk do not have an
equivalent clang flag. As per 1952442 comment 59 we can remove
the flags that are not supported by clang.
-Fixed compilation errors in cuda apps projects.
-Changes for copying libc++_shared.so on the target device.
-Disabled warnings in output
-xutils compiles with clang and not clang++.
-Disabled unused parameter flag for thrust.
-Added a WAR for CUDA GDB to continue using Android NDK r13b.
Raised Bug 200391744 which should remove this WAR and
provide the correct fix for it.
Reviewers - dpolyanitsa(cuda-gdb), lligowski(cufft), blelbach(thrust), tkashalikar(xutils), debalinab(apps and Makefile)

Bug 200368498

Reviewed by debalinab, dpolyanitsa, lligowski, blelbach, tkashalikar

Pressubmit testing DVS: http://builds4u.nvidia.com/dvs/#/change/2424104441897574.2?showTab=DVS

Jobs: 200368498-2006 200391744-2006
[git-p4: depot-paths = "//sw/gpgpu/thrust/": change = 24242616]

jaredhoberock/thrust,jaredhoberock/thrust,thrust/thrust,jaredhoberock/thrust,thrust/thrust,thrust/thrust,andrewcorrigan/thrust-multi-permutation-iterator,thrust/thrust,thrust/thrust,andrewcorrigan/thrust-multi-permutation-iterator,andrewcorrigan/thrust-multi-permutation-iterator,jaredhoberock/thrust,jaredhoberock/thrust