[harfbuzz] Upgrade pip (#15316)

Local build fails for me without this.

Author: behdad

projects/harfbuzz/Dockerfile

@@ -16,6 +16,7 @@
 
 FROM gcr.io/oss-fuzz-base/base-builder
 RUN apt-get update && apt-get install -y python3-pip ragel pkg-config zlib1g-dev:i386 && \
+    pip3 install --upgrade pip && \
     pip3 install meson==1.2.0 ninja
 RUN git clone --depth 1 https://github.com/harfbuzz/harfbuzz.git
 WORKDIR harfbuzz

projects/harfbuzz/build.sh

@@ -44,7 +44,7 @@ ninja -v -j$(nproc) -C $build test/fuzzing/hb-{shape,raster,vector,gpu,subset,re
 mv $build/test/fuzzing/hb-{shape,raster,vector,gpu,subset,repacker}-fuzzer $OUT/
 
 # Archive and copy to $OUT seed corpus if the build succeeded.
-mkdir all-fonts
+mkdir -p all-fonts
 for d in \
 	test/shape/data/in-house/fonts \
 	test/shape/data/aots/fonts \