install and use Ccache in Cygwin CI tasks

The Cygwin CI tasks come very close to the CI timeout ceiling, usually running
for close to an hour. It is hoped that this change (and upcoming caching) will
reduce this time, thus shortening the total CI time as these are the longest
running tasks at present.

diff --git a/ci/cygwin-build.sh b/ci/cygwin-build.sh
index c1cb28aabfa78bf6bac2e6544cad3592d22aec4c..2635fe680029a814678439c3287a69cd47aabf91 100644 (file)
--- a/ci/cygwin-build.sh
+++ b/ci/cygwin-build.sh
@@ -18,6 +18,11 @@ set -eux
 /cygwinsetup.exe --quiet-mode --wait --packages python3
 /cygwinsetup.exe --quiet-mode --wait --packages zlib-devel
 
+# setup Ccache to accelerate compilation
+/cygwinsetup.exe --quiet-mode --wait --packages ccache
+export CC="ccache ${CC:-cc}"
+export CXX="ccache ${CXX:-c++}"
+
 # use the libs installed with cygwinsetup instead of those in
 # https://gitlab.com/graphviz/graphviz-windows-dependencies
 export CMAKE_OPTIONS=-Duse_win_pre_inst_libs=OFF