These are the packages that would be merged, in order:

Calculating dependencies  ..... ....... done!
[ebuild  N    ] dev-java/eclipse-ecj-3.4-r2  USE="gcj java6" 0 kB 

Total: 1 package (1 new), Size of downloads: 0 kB


>>> Verifying ebuild manifests

>>> Emerging (1 of 1) dev-java/eclipse-ecj-3.4-r2
 * ecjsrc-3.4.zip RMD160 SHA1 SHA256 size ;-) ...                        [ ok ]
 * checking ebuild checksums ;-) ...                                     [ ok ]
 * checking auxfile checksums ;-) ...                                    [ ok ]
 * checking miscfile checksums ;-) ...                                   [ ok ]
>>> Unpacking source...
>>> Unpacking ecjsrc-3.4.zip to /var/tmp/portage/dev-java/eclipse-ecj-3.4-r2/work
>>> Source unpacked.
>>> Compiling source in /var/tmp/portage/dev-java/eclipse-ecj-3.4-r2/work ...
 * bootstrapping ecj with /usr/x86_64-pc-linux-gnu/gcc-bin/4.2.4/gcj -C ...
org/eclipse/jdt/internal/compiler/lookup/MethodVerifier15.java:755: error: Unrecognized character for encoding 'UTF-8'.
	// JLS 3 §8.4.5: more are accepted, with an unchecked conversion
                    ^
1 error
 * 
 * ERROR: dev-java/eclipse-ecj-3.4-r2 failed.
 * Call stack:
 *               ebuild.sh, line   49:  Called src_compile
 *             environment, line 3838:  Called die
 * The specific snippet of code:
 *       ${javac} ${javac_opts} $(find org/ -name '*.java') || die;
 *  The die message:
 *   (no error message)
 * 
 * If you need support, post the topmost build error, and the call stack if relevant.
 * A complete build log is located at '/var/tmp/portage/dev-java/eclipse-ecj-3.4-r2/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/dev-java/eclipse-ecj-3.4-r2/temp/environment'.
 * 
!!! When you file a bug report, please include the following information:
GENTOO_VM=  CLASSPATH="." JAVA_HOME="/etc/java-config-2/current-system-vm"
JAVACFLAGS="" COMPILER=""
and of course, the output of emerge --info

 * Messages for package dev-java/eclipse-ecj-3.4-r2:

 * 
 * ERROR: dev-java/eclipse-ecj-3.4-r2 failed.
 * Call stack:
 *               ebuild.sh, line   49:  Called src_compile
 *             environment, line 3838:  Called die
 * The specific snippet of code:
 *       ${javac} ${javac_opts} $(find org/ -name '*.java') || die;
 *  The die message:
 *   (no error message)
 * 
 * If you need support, post the topmost build error, and the call stack if relevant.
 * A complete build log is located at '/var/tmp/portage/dev-java/eclipse-ecj-3.4-r2/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/dev-java/eclipse-ecj-3.4-r2/temp/environment'.
 *