travis-ci: centralize ~/.buildman editing

Any time an x86 toolchain is used, we need to edit ~/.buildman to
reference it. Move the editing logic into a central place so that it
doesn't have to be duplicated everywhere that uses the x86 toolchain;
future patches will add additional cases where it's used.

It would be nice if we could unconditionally write all of ~/.buildman at
once. Unfortunately, buildman fails if any toolchain mentioned in a
toolchain-prefix entry doesn't exist, even if it doesn't need to use it
for the current build.

The sandbox/x86 build definition currently does nothing more than edit
~/.buildman; no builds are run. Fix this by not defining a custom script
for this build, and hence preventing that stanza from replacing the
default script.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Heiko Schocher <hs@denx.de>

.travis.yml

@@ -62,7 +62,10 @@ before_script:
   - if [[ "${TOOLCHAIN}" == *mips* ]]; then ./tools/buildman/buildman --fetch-arch mips ; fi
   - if [[ "${TOOLCHAIN}" == *or32* ]]; then ./tools/buildman/buildman --fetch-arch or32 ; fi
   - if [[ "${TOOLCHAIN}" == *sh4* ]]; then ./tools/buildman/buildman --fetch-arch sh4 ; fi
-  - if [[ "${TOOLCHAIN}" == *x86_64* ]]; then ./tools/buildman/buildman --fetch-arch x86_64 ; fi
+  - if [[ "${TOOLCHAIN}" == *x86_64* ]]; then
+      ./tools/buildman/buildman --fetch-arch x86_64;
+      echo -e "\n[toolchain-prefix]\nx86 = ${HOME}/.buildman-toolchains/gcc-4.9.0-nolibc/x86_64-linux/bin/x86_64-linux-" >> ~/.buildman;
+    fi
   - if [[ "${TOOLCHAIN}" == *xtensa* ]]; then ./tools/buildman/buildman --fetch-arch xtensa ; fi
 
 script:
@@ -104,8 +107,6 @@ matrix:
     - env:
         - BUILDMAN="sandbox x86"
           TOOLCHAIN="x86_64"
-      script:
-        - echo -e "\n[toolchain-prefix]\nx86 = ${HOME}/.buildman-toolchains/gcc-4.9.0-nolibc/x86_64-linux/bin/x86_64-linux-" >> ~/.buildman
     - env:
         - BUILDMAN="kirkwood"
     - env: