Disable cgo in builds

What does this MR do and why?

Previously the binaries linked against glibc, but this doesn't appear to be necessary. Building a static binary avoids the need to worry about OS glibc versions.

Before:

$ file devfile-gem
devfile-gem: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, Go BuildID=s8d8u7c2QXzZIDs0f9bl/ZfLMhEJU6bDKu2YuHSsR/sxofwIwe76xJ7nao8cid/cEJP0HV9k3bH_hfuYMyL, with debug_info, not stripped
$ ls -al devfile-gem
-rwxrwxr-x 1 stanhu stanhu 56737964 Apr 28 18:14 devfile-gem

After:

$ file devfile-gem
devfile-gem: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, Go BuildID=4l-h5orWkdrrB5B29Kp4/tF6zfK51c0EEdUWgHQ3N/e-meKO3Pzg0zhEQdOWt1/SzYoZbQbZv6SFyUdzcg7, with debug_info, not stripped
$ ls -al devfile-gem
-rwxrwxr-x 1 stanhu stanhu 56653447 Apr 28 18:14 devfile-gem

This is only an 84,517 byte difference.

Relates to gitlab-org/gitlab#524856 (closed)

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Before	After

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