Do not build or link to PCRE if QRegularExpression is disabled

Per Oswald's suggestion, just don't touch PCRE if it's not needed.
This can save ~500kB between text and data in QtCore.

Change-Id: Ia10c819c7fff562dda84ab0b77194baffbc8904e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

src/corelib/corelib.pro

@@ -31,6 +31,7 @@ ANDROID_PERMISSIONS = \
     android.permission.WRITE_EXTERNAL_STORAGE
 
 load(qt_module)
+load(qfeatures)
 
 include(animation/animation.pri)
 include(arch/arch.pri)
@@ -84,7 +85,6 @@ cmake_umbrella_config_version_file.input = $$PWD/../../mkspecs/features/data/cma
 cmake_umbrella_config_version_file.output = $$DESTDIR/cmake/Qt5/Qt5ConfigVersion.cmake
 
 load(cmake_functions)
-load(qfeatures)
 
 CMAKE_DISABLED_FEATURES = $$join(QT_DISABLED_FEATURES, "$$escape_expand(\\n)    ")
 

src/corelib/tools/tools.pri

@@ -43,7 +43,6 @@ HEADERS +=  \
         tools/qqueue.h \
         tools/qrect.h \
         tools/qregexp.h \
-        tools/qregularexpression.h \
         tools/qringbuffer_p.h \
         tools/qrefcount.h \
         tools/qscopedpointer.h \
@@ -100,7 +99,6 @@ SOURCES += \
         tools/qcontiguouscache.cpp \
         tools/qrect.cpp \
         tools/qregexp.cpp \
-        tools/qregularexpression.cpp \
         tools/qrefcount.cpp \
         tools/qshareddata.cpp \
         tools/qsharedpointer.cpp \
@@ -176,10 +174,15 @@ contains(QT_CONFIG,icu) {
     SOURCES += tools/qcollator_posix.cpp
 }
 
-pcre {
-    include($$PWD/../../3rdparty/pcre.pri)
-} else {
-    LIBS_PRIVATE += -lpcre16
+!contains(QT_DISABLED_FEATURES, regularexpression) {
+    HEADERS += tools/qregularexpression.h
+    SOURCES += tools/qregularexpression.cpp
+
+    pcre {
+        include($$PWD/../../3rdparty/pcre.pri)
+    } else {
+        LIBS_PRIVATE += -lpcre16
+    }
 }
 
 INCLUDEPATH += ../3rdparty/harfbuzz/src