sdl2.pc contains incorrect build prefix

[cgutman]

As of v0.7.1-engineering-release-wayland, the pkg-config file of for SDL2 contains an incorrect prefix path that is pointing to /opt/SDL/build/out instead of /usr or /usr/local (there are 2 copies of the SDL libraries, for some reason). As a result, building applications against SDL with pkg-config will fail due to being unable to find libraries and headers.

There also appears to be 2 copies of the incorrect sdl2.pc at /usr/lib/pkgconfig/sdl2.pc and /usr/local/lib/pkgconfig/sdl2.pc.

$ cat /usr/lib/pkgconfig/sdl2.pc
# sdl pkg-config source file

prefix=/opt/SDL/build/out
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: sdl2
Description: Simple DirectMedia Layer is a cross-platform multimedia library designed to provide low level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL, and 2D video framebuffer.
Version: 2.0.22
Requires:
Conflicts:
Libs: -L${libdir} -Wl,-rpath,${libdir} -Wl,--enable-new-dtags -lSDL2
Libs.private:  -lm -ldl -lpthread -lrt
Cflags: -I${includedir}/SDL2   -D_REENTRANT

Adjusting the prefix value to the proper installation directory fixes building SDL applications.