What happened

Android & iOS Configuration is failed at below line.

find_package(Qt5Widgets REQUIRED)

but desktop configuration works well.

Find Reason

I Checked each build settings(not modified, default value by Qt Creator) on Qt Creator. And Build Environment has differences about PATH.
Desktop build has Qt binary path(Qt/5.7/clang_64/bin). but Android & iOS Configuration hasn't it. Each configuration has toolchain path only.
ex-desktop)

/Volumes/Data2/Dev/Qt/5.7/clang_64/bin:/usr/bin:/bin:/usr/sbin:/sbin

ex-iOS)

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin

Possible fix

Append Qt binary path to PATH variable for Android & iOS default environment.
ex-iOS)

/Volumes/Data2/Dev/Qt/5.7/ios/bin:/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin

or Set CMAKE_PREFIX_PATH