Build break on GCC 6.3 Linux 64-bit

g++ -c -pipe -Wno-c++0x-compat -g -Og -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -Wall -W -Wno-c++0x-compat -Wvla -Wdate-time -Wshift-overflow=2 -Wduplicated-cond -Werror -Wno-error=cpp -Wno-error=deprecated-declarations -Wno-error=strict-overflow -D_REENTRANT -fPIC -DQT_NO_URL_CAST_FROM_STRING -DQT_NO_INTEGER_EVENT_COORDINATES -DQT_NO_FOREACH -DWTF_EXPORT_PRIVATE= -DJS_EXPORT_PRIVATE= -DENABLE_ASSEMBLER_WX_EXCLUSIVE=1 -DWTFReportAssertionFailure=qmlWTFReportAssertionFailure -DWTFReportBacktrace=qmlWTFReportBacktrace -DWTFInvokeCrashHook=qmlWTFInvokeCrashHook -DENABLE_LLINT=0 -DENABLE_DFG_JIT=0 -DENABLE_DFG_JIT_UTILITY_METHODS=1 -DENABLE_JIT_CONSTANT_BLINDING=0 -DBUILDING_QT__ -DWTF_USE_UDIS86=0 -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_BUILD_QML_LIB -DQT_BUILDING_QT -DQT_NO_CAST_TO_ASCII -DQT_ASCII_CAST_WARNINGS -DQT_MOC_COMPAT -DQT_USE_QSTRINGBUILDER -DQT_DEPRECATED_WARNINGS -DQT_DISABLE_DEPRECATED_BEFORE=0x050000 -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NETWORK_LIB -DQT_CORE_LIB -I. -Imemory -I. -Icompiler -I. -I../3rdparty/masm/jit -I../3rdparty/masm/assembler -I../3rdparty/masm/runtime -I../3rdparty/masm/wtf -I../3rdparty/masm/stubs -I../3rdparty/masm/stubs/wtf -I../3rdparty/masm -I../3rdparty/masm/disassembler -I../3rdparty/masm/disassembler/udis86 -Ijit -I. -I.generated -Ijsruntime -I. -Idebugger -Ianimations -I/home/jpnurmi/Projects/qt-59/qtbase/include -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtQml -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtQml/5.9.1 -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtQml/5.9.1/QtQml -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtCore/5.9.1 -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtCore/5.9.1/QtCore -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtNetwork -I/home/jpnurmi/Projects/qt-59/qtbase/include/QtCore -I.moc -I/home/jpnurmi/Projects/qt-59/qtbase/mkspecs/linux-g++ -o .obj/qv4isel_moth.o compiler/qv4isel_moth.cpp
In file included from compiler/qv4isel_moth_p.h:60:0,
                 from compiler/qv4isel_moth.cpp:41:
compiler/qv4instr_moth_p.h: In member function ‘virtual void QV4::Moth::InstructionSelection::callBuiltinPopScope()’:
compiler/qv4instr_moth_p.h:909:53: error: ‘*((void*)& call +4)’ is used uninitialized in this function [-Werror=uninitialized]
                  Size - sizeof(Instr::instr_common)); } \
                                                     ^
compiler/qv4isel_moth.cpp:1191:38: note: ‘call’ was declared here
     Instruction::CallBuiltinPopScope call;
                                      ^~~~
In file included from compiler/qv4isel_moth_p.h:60:0,
                 from compiler/qv4isel_moth.cpp:41:
compiler/qv4instr_moth_p.h: In member function ‘virtual void QV4::Moth::InstructionSelection::callBuiltinConvertThisToObject()’:
compiler/qv4instr_moth_p.h:909:53: error: ‘*((void*)& call +4)’ is used uninitialized in this function [-Werror=uninitialized]
                  Size - sizeof(Instr::instr_common)); } \
                                                     ^
compiler/qv4isel_moth.cpp:1344:49: note: ‘call’ was declared here
     Instruction::CallBuiltinConvertThisToObject call;
                                                 ^~~~
cc1plus: all warnings being treated as errors
Makefile:22709: recipe for target '.obj/qv4isel_moth.o' failed

7ed93899e9305ccd538361ee58baa4bf15ff8a41 is the first bad commit
commit 7ed93899e9305ccd538361ee58baa4bf15ff8a41
Author: Lars Knoll <lars.knoll@qt.io>
Date:   Wed May 10 09:42:18 2017 +0200

    Optimizations to the generated byte code
    
    Cut the size of the generated byte code in half, by storing
    parameters in a more compact form and always storing the
    instruction type in the instruction.
    
    We can still used computed goto's for a fast interpreter, by
    looking up the jump point for the next instruction in the jump
    table.
    
    Another advantage is that the byte code is now platform independent
    (modulo endianness).
    
    The change comes with a 3% performance impact on x86_64, which
    is acceptable considering the size savings on the bytecode.
    
    Change-Id: I37de3e1f94611987a85e65ea86536583aa965d6d
    Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

:040000 040000 9b23e123c3b2dfe6496c0e49b534fda204db64ba 47a91e41a6db3bf96d74b1ed310d99af9ac889bf M	src