Put "btoa" back into the built directories, since the underlying code

is now available in nss/lib.

security/nss/cmd/manifest.mn

@@ -39,6 +39,7 @@ REQUIRES = security nspr libdbm
 DIRS = lib  \
  zlib \
  atob  \
+ btoa  \
  certcgi \
  certutil  \
  checkcert  \
@@ -62,7 +63,6 @@ DIRS = lib  \
  $(NULL)
 
 TEMPORARILY_DONT_BUILD = \
- btoa  \
  SSLsample \
  modutil \
  $(NULL)