Add flock to OS X dependencies

Bump gcc to 11.1

- PR 94853 and PR 86153 are reoslved
- gfortran.dg/elemental_subroutine_3.f90 seems pass now.
- g++.dg/tls/thread_local4* added to allow list since they might random
  fail on qemu, and hard to reproduce.

Bump binutils to get rv32e fixes.

gitignore build directories

Bump Binutils to 2.36.1

Signed-off-by: Christoph Muellner <cmuellner@linux.com>

Bump gcc for testsuite fixes.

Bump qemu to 5.2.0

Bump glibc and linux kernel

 - RV32 require 5.10 which is too new for most linux distro.

Bump gdb for ctf related build fix.

Use `git rev-parse` to find .git dir

Otherwise, this code breaks if riscv-gnu-toolchain is itself a
submodule of another project. In that case the git config for this
tree will be $(srcdir)/../.git/modules/riscv-gnu-toolchain/config.

Automatic Nightly Release

Add new precompile process for rv32/64-elf toolchain: @higuoxing

1. repository activity check
2. change to build.yaml
3. assets layout
4. matrix action build
5. run daily too & build on PR
6. upload all assets to release
7. Only run nightly

[CI] Improve GitHub Action scripts.

This patch helps improve GitHub Action scripts.
 * Make CI happy again after d3dfbee6.
 * Simplify the logic of GH Action scripts using 'matrix'.
 * Add new precompile process for rv32/64-elf toolchain.

Add doc for development

Automatically download sub-module on-demand and add branch info.

 - It's too new to use, that require git 2.26+

 - So that we can build and clone in parallel.