common_target           = common_target
common_target.commands  = type $$shell_path($$PWD/foo.in) >> $$PWD/a.h $$escape_expand(\\n\\t) $$escape_expand(\\n\\t)
common_target.commands += type $$shell_path($$PWD/foo.in) >> $$PWD/b.h $$escape_expand(\\n\\t) $$escape_expand(\\n\\t)
common_target.commands += type $$shell_path($$PWD/foo.in) >> $$PWD/c.h $$escape_expand(\\n\\t) $$escape_expand(\\n\\t)
common_target.depends  = $$PWD/foo.in

a_target.target  = $$PWD/a.h
a_target.depends = common_target

b_target.target  = $$PWD/b.h
b_target.depends = common_target

c_target.target  = $$PWD/c.h
c_target.depends = common_target

PRE_TARGETDEPS += $$a_target.target $$b_target.target $$c_target.target $$common_target.target
QMAKE_EXTRA_TARGETS += a_target b_target c_target common_target