Allow building individual thirdparty components.
Allow building individual thirdparty components.

Now you can write:

./build_thirdparty -sasl -gflags

or similar to build individual thirdparty libaries, which is handy if
you're upgrading a single library or changing its build flags.

The behaviour with no command-line flags is the same as before this
patch, except that the 'git clean' is called only from the individual
library directories, rather than /thirdparty as before; this avoids
blowing away unchecked in directories while still removing build
artefacts as intended.

Change-Id: Iaafb6f6e42b0173c11eec3b08c8dea895dcd9199
Reviewed-on: http://gerrit.ent.cloudera.com:8080/725
Reviewed-by: Lenni Kuff <724b7df200764f5dc1b723c05ee6c6adabd11bb1@cloudera.com>
Tested-by: jenkins

michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala