Speed up build in Qt creator in common case

- Generate *.qm only when needed (and when qmake is run), this avoids a long qrc compile and link step every time
- Generate build.h every time, but only trigger link when it changed (like makefile.unix)

bitcoin-qt.pro

@@ -84,8 +84,8 @@ contains(BITCOIN_NEED_QT_PLUGINS, 1) {
 !windows || contains(USE_BUILD_INFO, 1) {
     genbuild.depends = FORCE
     genbuild.commands = cd $$PWD; share/genbuild.sh $$OUT_PWD/build/build.h
-    genbuild.target = genbuildhook
-    PRE_TARGETDEPS += genbuildhook
+    genbuild.target = $$OUT_PWD/build/build.h
+    PRE_TARGETDEPS += $$OUT_PWD/build/build.h
     QMAKE_EXTRA_TARGETS += genbuild
     DEFINES += HAVE_BUILD_INFO
 }
@@ -259,15 +259,14 @@ isEmpty(QMAKE_LRELEASE) {
     win32:QMAKE_LRELEASE = $$[QT_INSTALL_BINS]\\lrelease.exe
     else:QMAKE_LRELEASE = $$[QT_INSTALL_BINS]/lrelease
 }
-isEmpty(TS_DIR):TS_DIR = src/qt/locale
+isEmpty(QM_DIR):QM_DIR = $$PWD/src/qt/locale
 # automatically build translations, so they can be included in resource file
 TSQM.name = lrelease ${QMAKE_FILE_IN}
 TSQM.input = TRANSLATIONS
-TSQM.output = $$TS_DIR/${QMAKE_FILE_BASE}.qm
-TSQM.commands = $$QMAKE_LRELEASE ${QMAKE_FILE_IN}
+TSQM.output = $$QM_DIR/${QMAKE_FILE_BASE}.qm
+TSQM.commands = $$QMAKE_LRELEASE ${QMAKE_FILE_IN} -qm ${QMAKE_FILE_OUT}
 TSQM.CONFIG = no_link
 QMAKE_EXTRA_COMPILERS += TSQM
-PRE_TARGETDEPS += compiler_TSQM_make_all
 
 # "Other files" to show in Qt Creator
 OTHER_FILES += \