I personally have the following jni.h (which looks to correspond with your gcj version)

/usr/lib/gcc/i486-linux-gnu/4.1.2/include/jni.h

src/jni/org_gnu_libedataserver_ESourceGroup.c:10:17: error: jni.h: No such file or directory
In file included from src/jni/org_gnu_libedataserver_ESourceGroup.c:12:

So I guess that it doesn’t find jni.h

Running locate jni.h gives the following:

/usr/local/java/bea920/jdk150_04/include/jni.h
/usr/local/java/bea920/jrockit90_150_04/include/jni.h
/usr/local/java/j2sdk1.4.2_06/include/jni.h
/usr/local/java/bea816/jdk142_11/include/jni.h
/usr/local/java/bea816/jrockit81sp6_142_10/include/jni.h
/usr/local/java/bea815/jdk142_08/include/jni.h
/usr/local/java/bea815/jrockit81sp5_142_08/include/jni.h
/usr/local/java/jdk1.5.0_06/include/jni.h
/usr/local/java/jrockit-1.4.2_11/include/jni.h
/usr/lib/jvm/java-1.5.0-sun-1.5.0.06/include/jni.h
/usr/lib/j2sdk1.5-sun/include/jni.h
/usr/lib/gcc/i486-linux-gnu/4.1.0/include/jni.h

Which includes all the jdks installed on my Ubuntu box.

java -fullversion command gives the following:
java full version “gcj-1.4.2″

Why doesn’t it find jni.h?