[BUG] NDK still includes MIPS renderscript prebuilts

[enh]

i don't have r21 on my home machines, but r20 still contained 6.4MiB of unused MIPS prebuilts:

~/Downloads/android-ndk-r20b$ ls -l ./toolchains/renderscript/prebuilt/linux-x86_64/platform/mips
total 6516
-rwxr-xr-x 1 enh enh 1921120 Oct 17 15:34 libblasV8.so
-rw-r--r-- 1 enh enh  512680 Oct 17 15:34 libcompiler_rt.a
-rw-r--r-- 1 enh enh 1912352 Oct 17 15:34 libRScpp_static.a
-rw-r--r-- 1 enh enh  297820 Oct 17 15:34 librsrt.bc
-rwxr-xr-x 1 enh enh  408176 Oct 17 15:34 libRSSupportIO.so
-rwxr-xr-x 1 enh enh 1607172 Oct 17 15:34 libRSSupport.so
~/Downloads/android-ndk-r20b$ 

[enh-google]

i've uploaded the fixes (plural because we actually have three copies, one each for darwin, linux, and windows):

https://android-review.googlesource.com/c/platform/prebuilts/renderscript/host/windows-x86/+/1179842

https://android-review.googlesource.com/c/platform/prebuilts/renderscript/host/linux-x86/+/1179708

https://android-review.googlesource.com/c/platform/prebuilts/renderscript/host/darwin-x86/+/1179707

these were last updated in 2016, so i've not even bothered to find whether there's a script somewhere for regenerating them.

i did check the NDK build scripts, and it doesn't seem like we pay any attention to the contents of the directories (and i'm assuming presubmit will double check).

[enh-google]

looks like mips is already commented out in the prebuilts build script anyway: https://cs.corp.google.com/android/frameworks/rs/build_rs.py?q=build_rs.py&g=0&l=62

[enh-google]

fixed in master. a 10MiB saving doesn't seem worth backporting to r21, so will be fixed in r22.