Can not find files.

Hi
i am creating a custom widget plugin and integrate it to qt designer but when i build it , it gives following lines

Could Not Find E:\Custom_plugin-build-desktop\release\moc_mainwindow.cpp
del release\libCustom_plugin.a
Could Not Find E:\Custom_plugin-build-desktop\release\mainwindow.o
mingw32-make[1]: Leaving directory `E:/Custom_plugin-build-desktop'
del libCustom_plugin.a
Could Not Find E:\Custom_plugin-build-desktop\release\libCustom_plugin.a
Could Not Find E:\Custom_plugin-build-desktop\libCustom_plugin.a
The process "C:\QtSDK1\mingw\bin\mingw32-make.exe" exited normally.


My .pro file is as following

QT += core gui
CONFIG += designer plugin
TARGET = $$qtLibraryTarget($$TARGET)
TEMPLATE = lib
QTDIR_build:DESTDIR = $$QT_BUILD_TREE/plugins/designer
SOURCES = \
mainwindow.cpp \
custombutton.cpp
HEADERS = \
mainwindow.h \
custombutton.h \
defines.h
FORMS +=

target.path = $$[QT_INSTALL_PLUGINS]/designer
sources.files = $$SOURCES $$HEADERS *.pro
sources.path = $$[QT_INSTALL_EXAMPLES]/designer/Custom_plugin
INSTALLS += target sources

Thanks.