How to get full list names of depend libraries for static Qt5?

Like this:

./usr/bin/i686-w64-mingw32.static-pkg-config -libs Qt5Core

Add other Qt components if you need them. Full list of Qt5's pc files can be found in usr/i686-w64-mingw32.static/qt5/lib/pkgconfig/.

How to check "if(x86_64)"?

$(if $(findstring x86_64,$(TARGET)),your code,)

See src/openblas.mk

1)Fixed.
2)Enable x86_64 build, but don't copy dll-depends due to #589
3)I think that the best option would be to add Linux package nsis to http://mxe.cc/#requirements
4)#1143 (comment)
5)Installer disabled for x86_64_shared due to #589, Installer disabled for static builds because I don't know how to detect from NSIS at compile time is eiskaltdcpp-qt.exe 32-bit or 64-bit file. In order to detect 32-bit or 64-bit shared builds uses this: https://github.com/eiskaltdcpp/eiskaltdcpp/blob/master/windows/EiskaltDC%2B%2B.nsi#L3-L19, so I can detect static type if these two files don't exist simultaneously: libgcc_s_sjlj-1.dll, libgcc_s_seh-1.dll. But for static type I can't detect 32-bit or 64-bit case must be used to compile EiskaltDC++ installer.
6)Fixed.

3. Are you sure that system package nsis (e.g., from Debian) can build a 64-bit installer?

64-bit installer does not need. 32-bit installer completely provides all that is needed.

@pavelvat, I think it is generally a bad idea to add a package to requirements, if it is built by MXE and can be used. The main problem here is that targets of eiskaltdcpp and nsis are different. This could be fixed, should MXE allow a cross-target dependency.

Can we add the following syntax to _DEPS:

$(PKG)_DEPS     :=  gcc zlib bzip2  ... i686-w64-mingw32.static~nsis

?

The mechanism in #516 (Add mechanism for depending on build system packages) for cross-target deps would cause entire toolchain to be built again. This may be better handled in #961 (Build gcc once) and I've added a note there.

From https://github.com/Alexpux/MINGW-packages/pull/993:

The bug in 64-bit installers has finally been fixed upstream.

Bump cross-target dependency

Updated for Qt 5.6 and rebased.
Required multiCall from #1278:

        '$(TOP_DIR)/tools/copydlldeps.sh' -c \
                                          -d '$(PREFIX)/$(TARGET)/apps/$(PKG)/$(PKG)' \
                                          -F '$(PREFIX)/$(TARGET)/apps/$(PKG)/$(PKG)' \
                                          -F '$(PREFIX)/$(TARGET)/apps/$(PKG)/$(PKG)/sqldrivers' \
                                          -R '$(PREFIX)/$(TARGET)';

Current status:
1)Fixed
2)Fixed
3)required nsis for 64-bit mxe-targets (currently MXE contain nsis version 2.50, but version 2.51 is available https://sourceforge.net/projects/nsis/ and seems contain some fixes for 64-build)
4)Fixed
5)Fixed
6)Fixed
7)Not Fixed (#1104)

3. nsis: fix build for x86_64-w64-mingw32 targets #1340

Could you specify only really used qt modules?

Done.