add snap definition file

snap/snapcraft.yaml

@@ -0,0 +1,50 @@
+name: yosys
+base: core20
+version: '0.23'
+summary: yosys FPGA logic synthesis
+description: |
+  Pre-packaged logic synthesis tool for use with open source FPGA toolchains
+grade: devel
+confinement: classic
+
+build-packages:
+  - build-essential
+  - clang
+  - bison
+  - flex
+  - cmake
+  - git
+  - libreadline-dev
+  - gawk
+  - tcl-dev
+  - libffi-dev
+  - pkg-config
+  - python3
+  - libboost-system-dev
+  - libboost-python-dev
+  - libboost-filesystem-dev
+  - zlib1g-dev
+
+
+parts:
+  yosys:
+    source: https://github.com/YosysHQ/yosys.git
+    source-type: git
+    source-depth: 1
+    source-tag: yosys-0.23
+    plugin: make
+    make-parameters:
+      - all
+      - install
+    override-build: |
+      export PREFIX=/usr/
+      make config-gcc
+      snapcraftctl build
+    stage-packages:
+      - libtcl8.6
+      - graphviz
+      - xdot
+
+apps:
+  yosys:
+    command: usr/local/bin/yosys