qt-everywhere-src-5.15.1/qtbase/mkspecs/features/uikit/watchos_coretext.prf

# CoreText is documented to be available on watchOS, but the headers aren't present
# in the watchOS Simulator SDK like they are supposed to be. Work around the problem
# by adding the device SDK's headers to the search path as a fallback.
# rdar://25314492, rdar://27844864
simulator_system_frameworks = $$xcodeSDKInfo(Path, $${simulator.sdk})/System/Library/Frameworks
watchos:simulator:!exists($$simulator_system_frameworks/CoreText.framework/Headers/CoreText.h) {
    device_system_frameworks = $$xcodeSDKInfo(Path, $${device.sdk})/System/Library/Frameworks
    for (arch, QMAKE_APPLE_SIMULATOR_ARCHS) {
        QMAKE_CXXFLAGS += \
            -Xarch_$${arch} \
            -F$$simulator_system_frameworks \
            -Xarch_$${arch} \
            -F$$device_system_frameworks
    }
}