Added libonly option to meson

[rkd77]

I wanted only library for djgpp.
Compiler installed from rpm packages.

Here is the build script:

// mes.sh
rm -rf /tmp/builddir_qjs

PREFIX=/opt/qjs
DESTDIR=$HOME/qjs

LIBRARY_PATH="$PREFIX/lib"
PKG_CONFIG_PATH="$PREFIX/lib/pkgconfig"
C_INCLUDE_PATH="$PREFIX/include"
CFLAGS="-O2 -I$PREFIX/include"
CXXFLAGS="-O2 -I$PREFIX/include"
LDFLAGS="-L$PREFIX/lib"
meson setup /tmp/builddir_qjs --cross-file cross/linux-djgpp.ini \ -Dprefix=$PREFIX
-Dexamples=disabled
-Dlibc=false
-Dtests=disabled
-Dlibonly=true || exit 1

meson compile -C /tmp/builddir_qjs || exit 2

mkdir -p $DESTDIR
meson install -C /tmp/builddir_qjs --destdir $DESTDIR || exit 3

// linux-djgpp.ini
[binaries]
c = ['/usr/bin/i586-pc-msdosdjgpp-gcc', '-Wno-incompatible-pointer-types']
cpp = '/usr/bin/i586-pc-msdosdjgpp-g++'
objc = '/usr/bin/i586-pc-msdosdjgpp-gcc'
ar = '/usr/bin/i586-pc-msdosdjgpp-ar'
pkg-config = '/usr/bin/pkg-config'
strip = '/usr/bin/i586-pc-msdosdjgpp-strip'
exe_wrapper = '/bin/true'
ld = '/usr/bin/i586-pc-msdosdjgpp-ld'
cmake = '/usr/bin/cmake'

[properties]
root = '/usr/i586-pc-msdosdjgpp'
need_exe_wrapper = false

[host_machine]
system = 'dos'
cpu_family = 'x86'
cpu = 'i586'
endian = 'little'

[cmake]

CMAKE_BUILD_WITH_INSTALL_RPATH = 'ON'
CMAKE_FIND_ROOT_PATH_MODE_PROGRAM = 'NEVER'
CMAKE_FIND_ROOT_PATH_MODE_LIBRARY = 'ONLY'
CMAKE_FIND_ROOT_PATH_MODE_INCLUDE = 'ONLY'
CMAKE_FIND_ROOT_PATH_MODE_PACKAGE = 'ONLY'

[saghul]

Thank you! I'm going to hold off a bit since we have a larger PR modifying the meson build system currently in review and I think conflicts will arise.