Install for local user

mkdir kdevgit
cd kdevgit
git clone git://anongit.kde.org/kdevplatform
git clone git://anongit.kde.org/kdevelop
cd kdevplatform
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX=$HOME/kdevelop4 ..
make && make install

the following line is needed so that kbuildsycoca4 finds all .desktop files

export KDEDIRS=$HOME/kdevelop4:/usr
kbuildsycoca4
cd ../..
cd kdevelop
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX=$HOME/kdevelop4 ..
make && make install
kbuildsycoca4

Please note: Whenever you do some package or distribution update that calls kbuildsycoca4, you need to execute the following lines after the update:

export KDEDIRS=$HOME/kdevelop4:/usr
kbuildsycoca4