Fix FFmpeg build with x265

x265 does not generate pkg-config files unless it is on the latest Git tag.
This causes the FFmpeg build to fail later on.

Author: Unrud

Dockerfile

@@ -32,6 +32,8 @@ FROM emsdk-base AS x265-builder
 ENV X265_BRANCH=3.4
 ADD https://github.com/ffmpegwasm/x265.git#$X265_BRANCH /src
 COPY build/x265.sh /src/build.sh
+# Workaround for x265 not generating pkg-config unless on the latest Git Tag
+RUN rm -r .git
 RUN bash -x /src/build.sh
 
 # Build libvpx