remove pointless checking/fallback code for $$TARGET

qmake always sets that variable, so unless somebody pro-actively screws
it up (which doesn't seem like being worth checking for), it will just
work.

Change-Id: I3c4ada47cbd34ac68695d8efbf09c605392616f5
Reviewed-by: Joerg Bornemann <joerg.bornemann@nokia.com>

mkspecs/features/qt_module_config.prf

@@ -9,7 +9,6 @@
 load(qt_build_config) # loads qmodule.pri if hasn't been loaded already
 
 isEmpty(MODULE):MODULE = $$section($$list($$basename(_PRO_FILE_)), ., 0, 0)
-isEmpty(TARGET):error("You must set TARGET before include()'ing $${_FILE_}")
 isEmpty(VERSION):VERSION = $$QT_VERSION
 
 # Compile as shared/DLL or static according to the option given to configure

mkspecs/features/qt_tool.prf

@@ -15,7 +15,6 @@ INSTALLS += target
 # qtPrepareTool() to work with the non-installed build.
 !build_pass:!exists($$[QT_INSTALL_PREFIX]/.qmake.cache) {
 
-    isEmpty(TARGET):TARGET = $$section($$list($$basename(_PRO_FILE_)), ., 0, 0)
     isEmpty(MODULE):MODULE = $$TARGET
 
     MODULE_DEPENDS = $$replace(QT, -private$, )