set buildtype for WSLGd (#269)

Co-authored-by: Hideyuki Nagase <[email protected]>

Author: hideyukn88

Dockerfile

@@ -232,7 +232,8 @@ ENV CXX=/usr/bin/clang++
 # Build WSLGd Daemon
 COPY WSLGd /work/WSLGd
 WORKDIR /work/WSLGd
-RUN /usr/bin/meson --prefix=${PREFIX} build && \
+RUN /usr/bin/meson --prefix=${PREFIX} build \
+        --buildtype=${BUILDTYPE} && \
     ninja -C build -j8 install
 
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