I'm not certain that this is what fixed the problem, but after looking through the README's I did (on Ubunutu) "sudo apt-get install astyle" and then the recompile worked. I'm pretty sure that the check at the beginning of the Forge installation said that it found astyle even before I installed, although apt-get definitely acted like it was not already installed. Curious if someone familiar with what astyle is used for can confirm/deny that this could have been related to the issue that I was seeing.
I recently downloaded and attempted to install the "recommended" build of Forge src on both Windows and Linux (separate computers). The Windows installation worked fine, but the Linux installation resulted in 88 compile errors during the recompilation stage. I tried both the "recommended" build (611) and the "latest" build (622) with the same result on both. My process was pretty straightforward, extract the downloaded archive to a new folder and run "install.sh" (after doing a chmod +x install.sh). Selected output near the top of the errors: > Recompiling '"javac" -encoding UTF-8 -Xlint:-options -deprecation -g -source 1.6 -target 1.6 -classpath "lib:lib/...' failed : 1 == ERRORS FOUND == src/minecraft/net/minecraft/block/Block.java:242: error: cannot find symbol @SideOnly(Side.CLIENT) ^ symbol: class SideOnly location: class Block My "javac" version is "javac 1.7.0_07"