Portfile redaction question

[vincent habchi]

Hi there,

for an upcoming port (qgis), I need to tweak the build process. The  
building process unfolds this way: extract, create a build directory  
at the base of the extract tree, cd into it and call "cmake ..".

So I wrote this:

post-extract	{
	system  	"cd ${worksrcpath} && mkdir build"
	worksrcdir	${worksrcdir}/build
}

It works like a charm for a standard monolithic install (port  
install). But if I do it in two phases (e.g. port configure then port  
build), it fails, because the post-extract block is not executed  
twice, so ${worksrcdir} value is wrong during port build.

Is there any elegant way to solve this?

Thanks,
Vincent