enhance(libllvm) Using relative path for sysroot.

[MohammedKHC0]

This makes us one step closer to achieve dynamic prefix. (#24407)
A relative path for the sysroot was first discussed on WebAssembly/wasi-sdk#58
And got implemented on the upstream libllvm back in 2020 https://reviews.llvm.org/D76653

[MohammedKHC0]

ERROR: Version mismatch between libllvm and flang. libllvm=20.1.7:1, flang=20.1.7:0
Should i apply TERMUX_PKG_REVISION to flang as well? I guess so.
Edit: I added it to flang.

[robertkirkman]

Very good idea! I really think this is a very cool idea and I hope it works.

There is just one potential problem, which is that I am pretty sure some applications that are packaged in Termux cannot work properly if there are relative paths in some of their internal directories.

When it finishes I will try testing your PR and I will let you know what happens and if anything has an error!

[MohammedKHC0]

@robertkirkman Glad that you liked the idea.

There is just one potential problem, which is that I am pretty sure some applications that are packaged in Termux cannot work properly if there are relative paths in some of their internal directories.

I think that there should be no problems because llvm automaticlly converts the sysroot to absolute path.
From https://reviews.llvm.org/D76653#change-zuw0O32XbYXO:

if ((!SysRoot.empty()) && llvm::sys::path::is_relative(SysRoot)) {
    // Prepend InstalledDir if SysRoot is relative
    SmallString<128> P(InstalledDir);
    llvm::sys::path::append(P, SysRoot);
    SysRoot = std::string(P);
}

SysRoot is set to the absolute path. So there shouldn't be any side effects.
But feel free to correct me if i am wrong.

[MohammedKHC0]

The CI finally finished .. After only 5 hours 🥴

[TomJo2000]

The CI finally finished .. After only 5 hours 🥴

That is to be expected.

[robertkirkman]

I have tested this with building some packages on-device and some software both with and without build-package.sh, and I actually don't see any problems introduced by this. Good job!

I thought at first that these commands might be able to produce a problem:

cd $HOME
mkdir -p code
cd code
cp $PREFIX/bin/clang-20 .
./clang-20 -c test.c

however, those commands currently produce an error no matter whether this PR is used or not, so if this PR helps you, it is good since it doesn't seem to break anything I have found so far.

[finagolfin]

Bit busy right now, give me some time to look into this next week.