Add host_libdir to the LD_LIBRARY_PATH (#136)

* Add host_libdir to the LD_LIBRARY_PATH

This may be needed to run tools included in a HostBuildDependency,
as in Qt6.

* Update src/Runner.jl

Co-authored-by: Mosè Giordano <giordano@users.noreply.github.com>

src/Runner.jl

@@ -915,6 +915,8 @@ function platform_envs(platform::AbstractPlatform, src_name::AbstractString;
  "/lib64:/lib",
  # Add our CSL libraries for all architectures that can natively run within this environment
  csl_paths(host_platform),
+ # Libdir of the host platform, to run programs in `HostBuildDependency`
+ "$(host_libdir)",
  # Add our target/host-specific library directories for compiler support libraries
  target_lib_dir(host_platform),
  target_lib_dir(platform),