Replace PMM with vcpkg.json generation + bootstrapping

[mrexodia]

PMM is awfully complicated and does not work properly. Replace it with modern vcpkg.

[project]
name = "my_project"
version = "1.2"

[vcpkg]
version = "2021.05.12"
packages = ["fmt", "sqlite3"]

Should generate vcpkg.json (take care of the vcpkg identifiers not allowing capital letters or underscores):

{
  "name": "vcpkg_template",
  "version": "0.0.1",
  "dependencies": ["fmt", "sqlite3"]
}

And (right after the project):

include(FetchContent)

message(STATUS "Fetching vcpkg...")
FetchContent_Declare(
	vcpkg
	URL
		https://github.com/microsoft/vcpkg/archive/refs/tags/2021.05.12.tar.gz
)
FetchContent_MakeAvailable(vcpkg)

include(${vcpkg_SOURCE_DIR}/scripts/buildsystems/vcpkg.cmake)

See: https://github.com/build-cpp/vcpkg_template/tree/simplified-vscode. It also needs some kind of handling for subprojects (that scenario is not supported by vcpkg according to one of the authors) and it would be best if you get error messages that certain packages need to be specified in the root project for it to work.

[MoAlyousef]

Hi
I've created a new branch called "manifest" with support for vcpkg manifest mode. I chose (& vendored) nlohmann/json for vcpkg.json generation. I think the next step is to also support versions and features for each dependency:

{
  "$schema": "https://raw.githubusercontent.com/microsoft/vcpkg/master/scripts/vcpkg.schema.json",
  "name": "my-application",
  "version": "0.15.2",
  "dependencies": [
    "boost-system",
    {
      "name": "cpprestsdk",
      "default-features": false
    },
    "libxml2",
    "yajl"
  ]
}

[mrexodia]

Awesome, I’ll take a look! Maybe open a PR so it’s easier to review?