amend build to build s-cargot from sources

.travis.yml

@@ -9,6 +9,8 @@ before_install:
   - export TOWER_REPO=$PWD/tower
   - git clone https://github.com/galoisinc/ivory-tower-stm32
   - export BSP_REPO=$PWD/ivory-tower-stm32
+  - git clone https://github.com/aisamanra/s-cargot
+  - export SCARGOT_REPO=$PWD/s-cargot
 install:
   - cabal install cabal-install
   - cabal install alex
@@ -17,7 +19,7 @@ script:
   - ghc --version
   - cabal --version
   - arm-none-eabi-gcc --version
-  - IVORY_REPO=$IVORY_REPO TOWER_REPO=$TOWER_REPO BSP_REPO=$BSP_REPO make create-sandbox
+  - SCARGOT_REPO=$SCARGOT_REPO IVORY_REPO=$IVORY_REPO TOWER_REPO=$TOWER_REPO BSP_REPO=$BSP_REPO make create-sandbox
   - IVORY_REPO=$IVORY_REPO TOWER_REPO=$TOWER_REPO BSP_REPO=$BSP_REPO make
   - IVORY_REPO=$IVORY_REPO TOWER_REPO=$TOWER_REPO BSP_REPO=$BSP_REPO make test
 ghc:

Makefile

@@ -1,4 +1,5 @@
 
+SCARGOT_REPO ?= ../s-cargot
 IVORY_REPO ?= ../ivory
 
 default:
@@ -6,6 +7,7 @@ default:
 
 create-sandbox:
 	cabal sandbox init
+	cabal sandbox add-source $(SCARGOT_REPO)
 	cabal sandbox add-source $(IVORY_REPO)/ivory-artifact
 	cabal install --dependencies-only