[CI] Make sure that we use LLVM 11.0.1 rather than 11.1.0

The release/11.x branch of llvm-project has recently been update and now
contains LLVM 11.1.0. Until recently it's been LLVM 11.0.0. This is
fine, but llvm-tutor should just stick to one version. In order to
guarantee this, use tags rather than branches to get a particular
version of LLVM.

I switched to `git clone --depth 10`. 10 is an arbitrary number here -
big enough to guarantee that the `llvmorg-11.0.1` tag is also
downloaded.

.github/workflows/x86-darwin-llvm-from-sources.yml

@@ -3,6 +3,7 @@ name: x86-Darwin-llvm-from-sources
 on:
   schedule:
     - cron:  '0 0 * * *'
+  workflow_dispatch:
 
 jobs:
   build:
@@ -28,9 +29,9 @@ jobs:
         run: |
           # Adding the location of Ninja to $PATH
           export PATH=$GITHUB_WORKSPACE:$PATH
-          git clone --depth 1 --single-branch --branch release/11.x https://github.com/llvm/llvm-project
+          git clone --depth 10 --single-branch --branch release/11.x https://github.com/llvm/llvm-project
           cd llvm-project
-          git checkout release/11.x
+          git checkout tags/llvmorg-11.0.1
           mkdir build && cd build
           cmake -G Ninja -D CMAKE_MAKE_PROGRAM=$GITHUB_WORKSPACE/ninja \
             -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" \

.github/workflows/x86-ubuntu-llvm-from-sources.yml

@@ -29,9 +29,9 @@ jobs:
         run: |
           # Adding the location of Ninja to $PATH
           export PATH=$GITHUB_WORKSPACE:$PATH
-          git clone --depth 1 --single-branch --branch release/11.x https://github.com/llvm/llvm-project
+          git clone --depth 10 --single-branch --branch release/11.x https://github.com/llvm/llvm-project
           cd llvm-project
-          git checkout release/11.x
+          git checkout tags/llvmorg-11.0.1
           mkdir build && cd build
           ln -s /usr/bin/x86_64-linux-gnu-ld.gold ld
           cmake -G Ninja -D CMAKE_MAKE_PROGRAM=$GITHUB_WORKSPACE/ninja \

README.md

@@ -155,7 +155,7 @@ on Linux and Mac OS X:
 ```bash
 git clone https://github.com/llvm/llvm-project.git
 cd llvm-project
-git checkout release/11.x
+git checkout tags/llvmorg-11.0.1
 mkdir build
 cd build
 cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD=host -DLLVM_ENABLE_PROJECTS=clang <llvm-project/root/dir>/llvm/