rendertarget_gl: check for framebuffer object support earlier
rendertarget_gl: check for framebuffer object support earlier

Checks for framebuffer object support before creating the resolve fbo
instead of silently skipping the resolve (blit) operation in
ngli_rendertarget_gl_end_pass().

gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl