Fix missing error libgccjit in CI

src/ci/docker/host-x86_64/x86_64-gnu-llvm-15/Dockerfile

@@ -24,6 +24,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
  xz-utils \
  nodejs \
  mingw-w64 \
+ libgccjit-12-dev \
  && rm -rf /var/lib/apt/lists/*
 
 # Install powershell (universal package) so we can test x.ps1 on Linux
@@ -34,6 +35,9 @@ RUN curl -sL "https://github.com/PowerShell/PowerShell/releases/download/v7.3.1/
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+# Make `libgccjit.so` accessible.
+RUN ln -s /usr/lib/gcc/x86_64-linux-gnu/12/libgccjit.so /usr/lib/x86_64-linux-gnu/libgccjit.so
+
 # We are disabling CI LLVM since this builder is intentionally using a host
 # LLVM, rather than the typical src/llvm-project LLVM.
 ENV NO_DOWNLOAD_CI_LLVM 1