Meson: Don't use undocumented -export-dynamic option
GNU libtool is documented to support -export-dynamic and GNU ld is documented to support --export-dynamic. However, GCC isn't documented to support them. While GCC does support -export-dynamic for backwards compatibility, Clang doesn't support it and interprets it wrongly. This causes warnings to be shown during linking because Clang splits it into '-e xport-dynamic' and the linker can't find 'xport-dynamic' symbol.
This fixes warnings when compiling with Clang.
[268/525] Linking target providers/skel-implementation/capi/libgda-capi.so.
/usr/bin/ld: warning: cannot find entry symbol xport-dynamic; defaulting to 0x10000
[367/525] Linking target providers/postgres/libgda-postgres-6.0.so.
/usr/bin/ld: warning: cannot find entry symbol xport-dynamic; defaulting to 0x2B000
[377/525] Linking target providers/mysql/libgda-mysql-6.0.so.
/usr/bin/ld: warning: cannot find entry symbol xport-dynamic; defaulting to 0x23000This merge request also removes the unused find_library('dl') call in meson.build.