cras: Use --enable-fuzzer to pass -DHAVE_FUZZER=1 (#9308)

https://crrev.com/c/4123919 caused -Werror,-Wmacro-redefined, due to
./configure passing -DHAVE_FUZZER=0 when not configured with
--enable-fuzzer.

To fix that:
1. Use ./configure --enable-fuzzer instead of -DHAVE_FUZZER to avoid
multiple definitions of the macro.
2. The default make rule would try to build the fuzzer itself. So
instead we selectively build just the cras binary, which is enough to
produce libcrasserver.a and libcras_rust.a.
3. The build dependency of cras_dbus_bindings.h in the Makefile is not
properly specified, so we build it manually first.

Fixes https://crbug.com/oss-fuzz/54641.

projects/cras/build.sh

@@ -25,8 +25,9 @@ cd ${SRC}/adhd/cras
 ./git_prepare.sh
 mkdir -p ${WORK}/build && cd ${WORK}/build
 export CARGO_BUILD_TARGET="x86_64-unknown-linux-gnu"
-CFLAGS="${CFLAGS} -DHAVE_FUZZER" ${SRC}/adhd/cras/configure --disable-featured
-make -j$(nproc)
+CFLAGS="${CFLAGS}" ${SRC}/adhd/cras/configure --enable-fuzzer --disable-featured
+make -C src common/cras_dbus_bindings.h
+make -C src -j$(nproc) cras
 cp ${WORK}/build/src/server/rust/target/${CARGO_BUILD_TARGET}/release/libcras_rust.a /usr/local/lib
 
 CRAS_FUZZERS="rclient_message cras_hfp_slc cras_fl_media_fuzzer"
@@ -35,6 +36,7 @@ for fuzzer in ${CRAS_FUZZERS};
 do
 $CXX $CXXFLAGS $FUZZER_LDFLAGS \
   ${SRC}/adhd/cras/src/fuzz/${fuzzer}.cc -o ${OUT}/${fuzzer} \
+  -D HAVE_FUZZER=1 \
   -I ${SRC}/adhd/cras/src/server \
   -I ${SRC}/adhd/cras/src/common \
   $(pkg-config --cflags dbus-1) \