QIR Runtime: LLVM version discrepancy

[dime10]

Describe the bug

The QIR Runtime readme lists the required LLVM version as 11.0.0, while the prereq installation script uses version 11.1.0.

[bettinaheim]

@kuzminrobin Could you please update the readme as needed? Thanks!

[kuzminrobin]

@swernli, is it intentional or accidental that on Win the script installs clang 11.1.0 rather than 11.0.0?
If intentional, then can you please provide some more details about the reason?
(blame and PR for your convenience)

[swernli]

@kuzminrobin It is intentional and makes sure the versions are the same across platforms. Chocolatey by default installs the latest major version that has been verified, which is now 12.0. However, we ran into issues compiling QIR with Clang 12.0 (which makes sense because right now we use the LLVM 11 libraries to produce QIR). So we want to use the latest version of LLVM 11, 11.1.0. With chocolatey, we must specify this version explicitly. On Unix, apt-get of clang-11 will pick the latest version 11, also 11.1.0.