Refine bors command

[messense]

amd64 --target aarch64

[messense]

bors try-

[messense]

bors try amd64 --target armv7

[bors[bot]]

try

Build failed:

• conclusion

[messense]

bors r+ amd64 --target armv7

[bors[bot]]

Build failed:

• conclusion

[messense]

bors r+

[bors[bot]]

Build failed:

• conclusion

[messense]

bors r+

[bors[bot]]

Build failed:

• conclusion

[messense]

bors r+

[bors[bot]]

Build failed:

• conclusion

[messense]

bors try amd64 --target armv7

[bors[bot]]

try

Build failed:

• conclusion

[messense]

bors r+

[bors[bot]]

Build succeeded:

• conclusion