I'm trying compile libva 32bit on 64 bit system
and from ./configure command:

#---------------------------
...
configure: error: Package requirements (libdrm >= 2.4) were not met:

No package 'libdrm' found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables DRM_CFLAGS
and DRM_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.
#---------------------------

#------------------
$ cat /usr/lib/pkgconfig/libdrm.pc
prefix=/usr/local
exec_prefix=${prefix}
libdir=/usr/lib
includedir=/usr/include

Name: libdrm
Description: Userspace interface to kernel DRM services
Version: 2.4.66
Libs: -L${libdir} -ldrm
Cflags: -I${includedir} -I${includedir}/libdrm
#------------------

#--------
$ ls /usr/lib/*drm*
/usr/lib/libdrm_amdgpu.so@        /usr/lib/libdrm_nouveau.so.1.0.0*
/usr/lib/libdrm_amdgpu.so.1@      /usr/lib/libdrm_radeon.so@
/usr/lib/libdrm_amdgpu.so.1.0.0*  /usr/lib/libdrm_radeon.so.1@
/usr/lib/libdrm_intel.so@         /usr/lib/libdrm_radeon.so.1.0.1*
/usr/lib/libdrm_intel.so.1@       /usr/lib/libdrm.so@
/usr/lib/libdrm_intel.so.1.0.0*   /usr/lib/libdrm.so.2@
/usr/lib/libdrm_nouveau.so@       /usr/lib/libdrm.so.2.4.0*
/usr/lib/libdrm_nouveau.so.1@
#--------

If is something wrong with configure (I dont know)
 how use DRM_CFLAGS ?
I tried 
#-----------
./configure --disable-static --enable-glx \
  --libdir=/usr/lib \
  --bindir=/usr/bin32 \
  DRM_CFLAGS=/usr/lib \
  --includedir=/usr/include 
#-----------
 but not working.