Add a way to ignore headers for installation

[SirLynix]

Is your feature request related to a problem? Please describe.

Some headers are only used internally, but yet are used by the project and we want those in generated projects (VS solution for example).

For example:

	-- Add header and source files
	local headerExts = {".h", ".hpp", ".inl", ".natvis"}
	for _, ext in ipairs(headerExts) do
		add_headerfiles("include/(Nazara/" .. name .. "/**" .. ext .. ")")
		add_headerfiles("src/Nazara/" .. name .. "/**" .. ext)
	end

However since some headers are private, they shouldn't be installed.

Describe the solution you'd like

A way to tell add_headerfiles to simply not install those headers, for example:

add_headerfiles("src/**.hpp", { private = true })

which would add it to projects but not install them.

Describe alternatives you've considered

Currently I'm using { prefixdir = "private" } which does separate private headers from actual one.

But that folder still gets installed.

Additional context

No response

[waruqi]

The default mode for all add_/set_ interfaces is private, so setting {private = true} doesn't seem to change anything.

target:get("headerfiles") can always get all values.

[SirLynix]

That's not what I meant, I meant a way to tell xmake to consider those header files but not install them, only take them into account for project generation for example.
Maybe something like add_headerfiles("src/**.hpp", { install = false }) would be more appropriate.

[waruqi]

That's not what I meant, I meant a way to tell xmake to consider those header files but not install them, only take them into account for project generation for example. Maybe something like add_headerfiles("src/**.hpp", { install = false }) would be more appropriate.

I have supported it.

[SirLynix]

It works great! Thank you.