NDK r21b released

[Dan Albert]

NDK r21b is now available in the stable channel of the SDK manager and for download from our wiki (updated to developer.android.com are pending and should be live soon).

This release includes quite a few fixes:

• Fixed debugging processes containing Java with gdb. Cherrypicked "gdb: Don't fault for 'maint print psymbols' when using an index", which fixes a bug that caused gdb to fail when debugging a process with Java. Pure C/C++ executables were fine, but this effectively broke all app debugging. The error from gdb that confirms you were affected by this was gdb-8.3/gdb/psymtab.c:316: internal-error: sect_index_text not initialized.
• Issue 1166: Rehid unwinder symbols all architectures.
• Issue 1173: Fix gdb python symbol missing issue on Darwin.
• Issue 1176: Fix strip failing with "File truncated" errors on Windows.
• Issue 1178: Revert changes to stdatomic.h to maintain compatibility with C's _Atomic type qualifier. Note that the C++ standard will likely mandate this breakage in the future. See P0943R4 for more details.
• Issue 1184: Fix Clang crash for x86_64.
• Issue 1198: Fix incorrect constant folding of long doubles on Windows.
• Issue 1201: Fixed issue in ndk-build that was causing APP_PLATFORM to be corrupted for API 30+ with LP64 ABIs.
• Issue 1203: libc++ prebuilts and CRT objects are no longer built as Neon.
• Issue 1205: Potential fixes for relocation out of range issues with LLD.
• Issue 1206: LLD support for --fix-cortex-a8.

Note that this release does not contain the fix for https://github.com/android/ndk/issues/1060 (notarization for macOS Catalina). That's still being worked on and we'll ship another release for that just as soon as the fix is available.