gdal: fix expat detection
gdal: fix expat detection

nielx/haikuports,koletzky/haikuports,Begasus/haikuports,koletzky/haikuports,miqlas/haikuports,moochris/haikuports,haikuports/haikuports,miqlas/haikuports,miqlas/haikuports,haikuports/haikuports,nielx/haikuports,koletzky/haikuports,nielx/haikuports,Begasus/haikuports,moochris/haikuports,haikuports/haikuports,Begasus/haikuports,haikuports/haikuports,moochris/haikuports,Begasus/haikuports,haikuports/haikuports,Begasus/haikuports