[many ports] Apply host dependencies

[ras0219]

Reopening of #15424.

This PR solves a long-standing issue with manifests being unable to correctly install boost while cross-compiling. This is done by enabling consumers to mark a dependency as coming from the host (via "host": true). The dependency can then be accessed in the portfile via ${CURRENT_HOST_INSTALLED_DIR}/subpath.

This PR does not automatically add any subpaths of the host installed dir to helpers such as vcpkg_configure_cmake(). For now, consumers are intended to use vcpkg_add_to_path() to pick individual required executable folders:

vcpkg_add_to_path(PREPEND "${CURRENT_HOST_INSTALLED_DIR}/tools/grpc")

See docs/users/tools.md for more details.

[strega-nil]

just some minor notes, not fully reviewed

[strega-nil]

Suggested change

	string(COMPARE EQUAL "${TARGET_TRIPLET}" "${HOST_TRIPLET}" I_AM_NOT_CROSSCOMPILING)

no reason to have this, imo

[autoantwort]

Not useful for users, but imho useful for maintainers. If you are writing a port that depends on itself with the host flag, you have to make distinctions if you are cross compiling or not. But an example like

if(NOT "${TARGET_TRIPLET}" STREQUAL "${HOST_TRIPLET}")
  # specific cross compile code
endif()

would be more helpful than the string example.

[autoantwort]

nvm this is the next line.

[autoantwort]

Is it a bug? But for me there is no variable ${HOST_TRIPLET} or the value is the empty string?

[autoantwort]

Is it a bug? But for me there is no variable ${HOST_TRIPLET} or the value is the empty string?

nwm. set(HOST_TRIPLET "${_HOST_TRIPLET}") gets introduced with this PR. I thought it is already there...

[Neumann-A]

better define VCPKG_(IS_)CROSSCOMPILING

[strega-nil]

Is there a reason that this is a draft?

[ras0219]

I wanted to ensure it builds cleanly before requesting review, since build breaks will likely mean changing the approach in one or more ports

[Neumann-A]

all ports using vcpkg_configure_qmake need an additional host dependency on qt5-base

[ras0219]

With this PR I'm specifically targeting this list:

vcpkg/scripts/azure-pipelines/test-modified-ports.ps1

Lines 139 to 145 in a44feca

	# WORKAROUND: the x86-windows flavors of these are needed for all cross-compilation, but they are not auto-installed.
	# Install them so the CI succeeds:
	if ($Triplet -in @('x64-uwp', 'arm64-windows', 'arm-uwp')) {
	.\vcpkg.exe install protobuf:x86-windows boost-build:x86-windows sqlite3:x86-windows yasm-tool:x86-windows ampl-mp:x86-windows @commonArgs
	} elseif ($Triplet -in @('x64-windows', 'x64-windows-static', 'x64-windows-static-md')) {
	.\vcpkg.exe install yasm-tool:x86-windows @commonArgs
	}

[autoantwort]

For the port boost-context and grpc the port version field was not updated

[Neumann-A]

another todo: all ADD_BIN_TO_PATH options vcpkg_(install|build)_* need to be disabled if target!=host
@ras0219-msft: I hope you keep a list with those ToDo's :)

[Neumann-A]

Hmm could it be that CURRENT_HOST_INSTALLED_DIR is not yet in vcpkg master?

[autoantwort]

Hmm could it be that CURRENT_HOST_INSTALLED_DIR is not yet in vcpkg master?

Yes it gets introduced with this PR. See scripts/ports.cmake

[Neumann-A]

hmm probably would make sense to split this PR up in two.
a) only provide the new/extra definitions
b) fix all the ports

a) could probably be merged way faster than b)

[ras0219]

The problem is really the changes to core helpers that provoke full rebuilds if any other core changes were merged; the handful of changed ports are insignificant here

[soumyamahunt]

This PR assumes there will be only one host triplet needed, what if multiple tools need be installed with multiple host triplet? For example, what if user wants to build contoso-code-generator for x86-windows triplet and contoso-build-system for x64-windows? Although I can't think of any port that requires such configuration, I think this could cause issues in future and would be nice to see this scenario to be addressed by this PR. My proposed solution would be to allow overriding host triplet per dependency, something like this:

{
    "name": "contoso-http-library",
    "version-string": "1.0.0",
    "description": "Contoso's http runtime library",
    "dependencies": [
        "contoso-core-library",
        {
            "name": "contoso-code-generator",
            "host": true,
            "host-triplet": "x86-windows"
        },
        {
            "name": "contoso-build-system",
            "host": true,
            "host-triplet": "x64-windows"
        }
    ]
}

Basically host-triplet combined with platform field can be used to handle any scenario for building dependencies with manifest.

[Neumann-A]

@soumyamahunt that was already discussed in #15424

[JackBoosY]

We also need to modify libvpx dependency yasm-tool.

[ras0219-msft]

another todo: all ADD_BIN_TO_PATH options vcpkg_(install|build)_* need to be disabled if target!=host

While using that is suspect, it would certainly be a breaking change to do that now. We may wish to add a warning in the future.