1. add -DECM_MKSPECS_INSTALL_DIR= to MSYS2_ARG_CONV_EXCL so mkspecs files are placed in /mingw{32,64} instead of /msys{32,64}/mingw{32,64}
2. change deprecated LIB_INSTALL_DIR with KDE_INSTALL_LIBDIR
3. place mkspecs files in ${QT5_PREFIX}/share/qt5/mkspecs (Qt5 mkspecs dir) instead of ${QT5_PREFIX} which points to root /mingw{32,64}
* upgrade some broken packages
* correct some broken urls/checksums
* use secure urls where possible
* update PKGBUILD templates
* remove line-ending whitespace
* minor typos/fixes
Remaining md5sums either didn't download or
didn't pass checksum tests.
The plugin gets built as a dll, since qt5-static/cmake doesn't
have support for building static plugins, though I could try
changing SHARED to PLUGIN to see if that fixes it.
