gnu: varnish: Fix build on i686-linux.

* gnu/packages/web.scm (varnish)[arguments]: When building for
i686-linux add a make-flag to adjust the CFLAGS.

Change-Id: I9dbd9566de33f2ad7445e3a7ee8bc2d01e430cc9

gnu/packages/web.scm

@@ -6509,6 +6509,10 @@ deployments.")
                                               (search-input-file %build-inputs
                                                                  "/bin/gcc"))
                                "--localstatedir=/var")
+       ,@(if (target-x86-32?)
+             '(#:make-flags
+               (list "CFLAGS+=-fexcess-precision=standard"))
+             '())
        #:phases
        (modify-phases %standard-phases
          (add-after 'unpack 'use-absolute-file-names