travis: Remove clang-3.8 build

The package appears to have been renamed in Ubuntu.  The only reason this test
is currently passing is because the hypervisor build falls back to clang, at
version 3.5

Add an explicit test in the build script that out desired compiler is
available.  Note that travis already performs this step, but in a way which
isn't fatal to the build.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by Doug Goldstein <cardoe@cardoe.com>

.travis.yml

@@ -22,12 +22,8 @@ matrix:
           env: XEN_TARGET_ARCH=x86_64 debug=y
         - compiler: clang
           env: XEN_TARGET_ARCH=x86_64 clang=y debug=n
-        - compiler: clang-3.8
-          env: XEN_TARGET_ARCH=x86_64 clang=y debug=n
         - compiler: clang
           env: XEN_TARGET_ARCH=x86_64 clang=y debug=y
-        - compiler: clang-3.8
-          env: XEN_TARGET_ARCH=x86_64 clang=y debug=y
         - compiler: gcc
           env: XEN_TARGET_ARCH=arm32 CROSS_COMPILE=arm-linux-gnueabihf- debug=n
         - compiler: gcc

scripts/travis-build

@@ -1,5 +1,7 @@
 #!/bin/bash -ex
 
+$CC --version
+
 # random config or default config
 if [[ "${RANDCONFIG}" == "y" ]]; then
     make -C xen randconfig