Fix xcb library name.
Fix xcb library name.

The name is wrong, so this only really worked if xcb was
actually linked normally, if the user opened it in another
way (dlopen) this would get missed.

Bug: b/139491466

Change-Id: Ib9a84bd7424a1c4bf027ecb9f1a5b9af6d7210b3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38368
Reviewed-by: Ben Clayton <1f693eb7158dc33015048c09d6712f74dabddf79@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>
Kokoro-Presubmit: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Tested-by: Andrew Woloszyn <2926f0436f8103ab8257713335cf26447d8bf68a@google.com>

google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader