Regularise the AWS CodeBuild Clang buildspecs

Check out the diff vs. buildspec.yml and you'll see these are now much more regular.
This duplication and drift is a vindication of Travis' "matrix" approach if you ask me ;)

Author: smowton

buildspec-linux-clang-3.8.yml

@@ -14,7 +14,6 @@ phases:
   build:
     commands:
       - echo Build started on `date`
-      - git submodule update --init --recursive
       - make -C src minisat2-download
       - make -C jbmc/src setup-submodules
       - make -C src CXX='ccache /usr/bin/clang++-3.8' CXX_FLAGS='-Qunused-arguments -DDEBUG'

buildspec-linux-clang.yml

@@ -16,15 +16,19 @@ phases:
   build:
     commands:
       - echo Build started on `date`
-      - git submodule update --init --recursive
-      - make -C src CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments'
-      - make -C jbmc/src CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments'
+      - make -C src minisat2-download
+      - make -C jbmc/src setup-submodules
+      - make -C src CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments' -j2
+      - make -C unit CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments' -j2
+      - make -C jbmc/src CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments' -j2
+      - make -C jbmc/unit CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments' -j2
   post_build:
     commands:
-      - make -C unit test CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments'
+      - make -C unit test
       - make -C regression test
+      - make -C regression/cbmc test-paths-lifo
       - env PATH=$PATH:`pwd`/src/solvers make -C regression/cbmc test-cprover-smt2
-      - make -C jbmc/unit test CXX='ccache /usr/bin/clang++-7' CXX_FLAGS='-Qunused-arguments'
+      - make -C jbmc/unit test
       - make -C jbmc/regression test
       - echo Build completed on `date`
 cache: