qtbase build fails if "make install" is run without "make" first

qtbase gives a linker error if "make install" is run before "make":

/home/al/rpi-ramdisk/packages/toolchain/bin/../lib/gcc/arm-linux-gnueabihf/4.9.3/../../../../arm-linux-gnueabihf/bin/ld: cannot find -lqtpcre
collect2: error: ld returned 1 exit status
Makefile:1229: recipe for target '../../lib/libQt5Core.so.5.8.1' failed
make[3]: *** [../../lib/libQt5Core.so.5.8.1] Error 1
make[3]: Leaving directory '/home/al/rpi-ramdisk/packages/qt/qtbase/src/corelib'
Makefile:202: recipe for target 'sub-corelib-install_subtargets' failed
make[2]: *** [sub-corelib-install_subtargets] Error 2
make[2]: Leaving directory '/home/al/rpi-ramdisk/packages/qt/qtbase/src'
Makefile:58: recipe for target 'sub-src-install_subtargets' failed
make[1]: *** [sub-src-install_subtargets] Error 2
make[1]: Leaving directory '/home/al/rpi-ramdisk/packages/qt/qtbase'

The build completes successfully if "make" is run first.