build: clean up config_fips.gypi

[danbev]

Currently when configuring the project using --openssl-fips a gyp
include file name config_fips.gypi will be created. If the project is
later configured but without the --openssl-fips flag an error will
occur. For example:

  $ ./configure --openssl-fips=bogus
  $ ./configure && make -j8
  ...
  /node/deps/openssl/fips/fipsld:
  line 8: /bin/fipsld: No such file or directory
  Error 127

This commit suggests removing the generate config_fips.gypi when the
--openssl-fips flag is not give on the command line.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

build