CircleCI : specialized caches (#798)

CircleCI: two cache save/restore mechanisms. One bound to musl-cross+patches, one for modules + patches.

* Replacing the generic cache bound to CircleCI user to have two caches levels. One for musl-cross and its patchsets, one for all modules and their patchset being the same. So if modules changed, we use the cache for musl-cross as a fallback to economize one hour of precious build time out of two, while most of Heads changes are on the scripts and can be built on top of packages+patches cache

.circleci/config.yml

@@ -11,14 +11,29 @@ jobs:
             apt install -y build-essential zlib1g-dev uuid-dev libdigest-sha-perl libelf-dev bc bzip2 bison flex git gnupg iasl m4 nasm patch python wget gnat cpio ccache pkg-config cmake libusb-1.0-0-dev autoconf texinfo ncurses-dev
       - checkout
 
-      - restore_cache:
-          key: heads-{{ .Environment.CIRCLE_USERNAME }}-{{ .Environment.CACHE_VERSION }}
-
       - run:
           name: git reset
           command: |
             git reset --hard "$CIRCLE_SHA1" \
 
+      - run:
+          name: Creating all modules and patches digest
+          command: |
+            find ./patches/ ./modules/ -type f | sort -h |xargs sha256sum > /tmp/all_modules_and_patches.sha256sums \
+
+      - run:
+          name: Creating musl-cross-make and musl-cross-make patches digest
+          command: |
+            find ./patches/musl-cross-* modules/musl-cross* -type f | sort -h | xargs sha256sum > /tmp/musl-cross_module_and_patches.sha256sums \
+
+
+      - restore_cache:
+          keys:
+            #Restore existing cache for modules checksums validated to be exactly the same as in github current commit
+            - heads-modules-and-patches-{{ checksum "/tmp/all_modules_and_patches.sha256sums" }}
+            #If precedent fails. Restore cache for musl-cross module checksum validated to be exactly the same as in github current commit
+            - heads-cross-musl-{{ checksum "/tmp/musl-cross_module_and_patches.sha256sums" }}
+
 # linuxboot steps need something to pass in the kernel header path
 # skipping for now
 #      - run:
@@ -153,12 +168,19 @@ jobs:
           path: build/qemu-coreboot
 
       - save_cache:
-          key: heads-{{ .Environment.CIRCLE_USERNAME }}-{{ .Environment.CACHE_VERSION }}
+          #Generate cache for the same musl-cross module definition if hash is not previously existing
+          key: heads-cross-musl-{{ checksum "/tmp/musl-cross_module_and_patches.sha256sums" }}
+          paths:
+            - crossgcc
+            - build/musl-cross-*
+
+      - save_cache:
+          #Generate cache for the exact same modules definitions if hash is not previously existing
+          key: heads-modules-and-patches-{{ checksum "/tmp/all_modules_and_patches.sha256sums" }}
           paths:
             - packages
             - crossgcc
             - build
-
 workflows:
   version: 2
   build_and_test: