[PATCH] ksba-config: more portable, using grep -F over fgrep

[NIIBE Yutaka]

Hello,

Thank you for your patch, I'm going to apply the change to libksba.
I'll also do similar to ntbtls.

By GnuPG related libraries, files for pkg-config (*.pc) are provided.
pkg-config (and compatible) can be used for general use cases.

To build GnuPG, gpgrt-config is used as replacement of gpg-error-config,
npth-config, libgcrypt-config, libassuan-config, ksba-config, and
ntbtls-config.

If possible, please consider updating your script(s) and please don't
keep using *-config (except gpgrt-config).
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