Conflicting library versions error is missed when using multiple hxmls

[tobil4sk]

If I compile with the following command:

haxe -lib haxelib:4.1.0 -lib haxelib:git --version

I get the expected error Error: Error: Cannot process `haxelib:git`: Library haxelib has two versions included : 4.1.0 and git.

However, if the -lib flags are contained between different hxmls, then haxelib is invoked once per hxml, which means it doesn't catch this error anymore:

haxe a.hxml b.hxml --version

# a.hxml
-lib haxelib:4.1.0

# b.hxml
-lib haxelib:git

This leads to a potentially broken compilation and headaches, as vshaxe reports version 4.1.0, but I might get compiler errors from the git version and really I have a mixture of modules and flags from both versions.

This seems to be a regression since 4.2, possibly due to: #10654.

The correct behaviour is for haxe to call haxelib once per compilation to resolve all libraries at once, which gives haxelib the chance to complain if library versions are conflicting.