Travis: Test bitmain-only build

.travis.yml

@@ -70,6 +70,8 @@ matrix:
       env: myCC='clang' EXTRA_DEPS='pkg-config libncursesw5-dev' CONFIGURE_ARGS='--disable-other-drivers --enable-opencl --enable-keccak --enable-scrypt --disable-adl'
     - compiler: ": Only bitforce"
       env: myCC='clang' UBUNTU_DEPS='linux-libc-dev' EXTRA_DEPS='pkg-config libncursesw5-dev' CONFIGURE_ARGS='--disable-other-drivers --enable-bitforce'
+    - compiler: ": Only bitmain"
+      env: myCC='clang' EXTRA_DEPS='pkg-config libncursesw5-dev' CONFIGURE_ARGS='--disable-other-drivers --enable-bitmain'
     - compiler: ": Only icarus"
       env: myCC='clang' EXTRA_DEPS='pkg-config libncursesw5-dev' CONFIGURE_ARGS='--disable-other-drivers --enable-icarus'
     - compiler: ": Only dualminer"