chore: Use a specific non-broken slimcc version.

fuhsnn/slimcc@7b7c986 broke it.

other/docker/slimcc/creduce.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+if ! gcc -I/work/c-toxcore/toxcore -fsyntax-only crash.c; then
+  exit 1
+fi
+/work/slimcc/slimcc -I/work/c-toxcore/toxcore -c crash.c 2>&1 | grep "file_exists: Assertion"

other/docker/slimcc/slimcc.Dockerfile

@@ -15,12 +15,28 @@ RUN apt-get update && \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/*
 
+# Uncomment this to find bugs in slimcc using creduce.
+#RUN apt-get update && \
+# DEBIAN_FRONTEND="noninteractive" apt-get install -y --no-install-recommends \
+# creduce \
+# && apt-get clean \
+# && rm -rf /var/lib/apt/lists/*
+
 WORKDIR /work/slimcc
-RUN ["git", "clone", "--depth=1", "https://github.com/fuhsnn/slimcc", "/work/slimcc"]
-RUN ["make", "CFLAGS=-O3"]
+RUN ["git", "clone", "https://github.com/fuhsnn/slimcc", "/work/slimcc"]
+# Comment this to checkout master (e.g. to find bugs using creduce).
+RUN ["git", "checkout", "ac9ddf4d39642e6b4880b1a73e19c6f2769d857e"]
+RUN ["make", "CFLAGS=-O3", "-j4"]
 
 WORKDIR /work/c-toxcore
 COPY --from=sources /src/ /work/c-toxcore
+
+# Uncomment this to find bugs in slimcc using creduce.
+#COPY other/docker/slimcc/creduce.sh /work/c-toxcore/other/docker/slimcc/
+#RUN cp toxcore/ccompat.h crash.c \
+# && other/docker/slimcc/creduce.sh \
+# && creduce other/docker/slimcc/creduce.sh crash.c
+
 COPY other/docker/slimcc/Makefile /work/c-toxcore/
 RUN ["make"]