undetectable libraries

[Juan carlos Rebate]

good evening, I have a strange problem, I try to compile code that
uses gtk3 and sdl2 in addition to curl, the problem is that when I
invoke the gcc compiler it tells me that sdl2-devel and libcurl are
not installed, but actually yes are.
./configure --cross-prefix=x86_64-w64-mingw32- --enable-sdl
--enable-gtk --enable-curl
I'm not sure if they allow to send screenshot to show windows of the
cygwin package installer so they can see the installed packages. How
could I find the variable and add it to compile?