Validate and build graph

[redlars]

Using latest version of vcpkg on Windows 10 Pro.

Two questions;

1. The command "vcpkg install gdal" needed to install 101 packages (which is fine). It ran for a LONG time but failed on package 93 because Oracle has dropped support for libmysql for 32-bit (which is also fine). It would have been nice to get this error earlier. Obvioulsy do not know the inner workings of vcpkg but a pre-validation step for all packages would be nice to catch any obvious issues.

2. It would be very helpful if vcpkg could output a "building graph" of a given package. The command "vcpkg install gdal" will list all 101 packages in a list but does not say anything about the relationship between each package. It does not tell me which package requires "boost-Phoenix".

[past-due]

I second 2 as a very useful feature addition.

There's obviously a limit to what can be done for 1, but a perhaps a "target-support" attribute in the CONTROL file that could specify target and/or architecture combinations?

So instead of having (for example) a check for "WindowsStore" inside the portfile.cmake for a port that doesn't yet support WindowsStore builds, the CONTROL file could specify:
Target-Support: !WindowsStore
(which would exclude WindowsStore / UWP builds, but implicitly allow anything else)

If a port doesn't support x86 / 32-bit builds, the CONTROL file could specify:
Target-Support: !x86
or
Target-Support: !32bit (which would exclude any 32-bit target)

Or, if a port doesn't support x86 Windows builds (but does support x64 Windows builds):
Target-Support: !Windows[x86]

Or for a port that supports all builds (including 64-bit macOS builds) but not 32-bit macOS builds:
Target-Support: !macOS[x86]

Alternatively, name it Target-Unsupported and omit the !?

[JackBoosY]

Hmm... I think this is a good suggestion, and we already added keyword Support in CONTROL.
Reserved.