Rename findNinja to findOrBuildNinja and fail early if gyp fails

We should not not use the $$ syntax to collect the output of the gyp
call instead we should just fail with an error in case gyp_qtwebengine
fails.

Change-Id: Ib6218bdfb998100a3717470713ed5bf5f30db339
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>

build/build.pro

@@ -5,11 +5,10 @@
 TEMPLATE = aux
 
 message(Running Gyp...)
-GYP_OUTPUT = $$system(python ./gyp_qtwebengine)
-message($$GYP_OUTPUT)
+!system(python ./gyp_qtwebengine): error("-- running gyp_qtwebengine failed --")
 
 ninja.target = invoke_ninja
-ninja.commands = $$findNinja() $$(NINJAFLAGS) -C $$getOutDir()/$$getConfigDir()
+ninja.commands = $$findOrBuildNinja() $$(NINJAFLAGS) -C $$getOutDir()/$$getConfigDir()
 ninja.depends: qmake
 QMAKE_EXTRA_TARGETS += ninja
 

build/qmake/mkspecs/features/functions.prf

@@ -71,7 +71,7 @@ defineReplace(which) {
   return($$out)
 }
 
-defineReplace(findNinja) {
+defineReplace(findOrBuildNinja) {
   !isEmpty(CACHED_NINJA_EXECUTABLE):exists($$CACHED_NINJA_EXECUTABLE): return($$CACHED_NINJA_EXECUTABLE)
   out = $$which(ninja)
   # Try to be smart about it if we know where the chromium sources are located

qtwebengine.pro

@@ -22,7 +22,7 @@ qtHaveModule(widgets) {
 SUBDIRS += examples
 
 # Ninja executable location needs to be determined early for extra targets. Should be fetched from cache most of the time anyway.
-NINJA_EXECUTABLE = $$findNinja()
+NINJA_EXECUTABLE = $$findOrBuildNinja()
 
 # Extra targets that invoke ninja on the desired configuration added for convenience
 release.target = release