Fix bazel build with gflags

The code references `@ac_cv_have_libgflags@` but not `@ac_cv_have_libgflags_h@`. This corrects that.

`int(with_gflags)` incorporates the possibility of `True/False`: https://github.com/bazelbuild/bazel/issues/4792

bazel/glog.bzl

@@ -94,18 +94,18 @@ sed -e 's/@ac_cv_cxx_using_operator@/1/g' \
     -e 's/@ac_cv_have_unistd_h@/1/g' \
     -e 's/@ac_cv_have_stdint_h@/1/g' \
     -e 's/@ac_cv_have_systypes_h@/1/g' \
-    -e 's/@ac_cv_have_libgflags_h@/1/g' \
+    -e 's/@ac_cv_have_libgflags@/{}/g' \
     -e 's/@ac_cv_have_uint16_t@/1/g' \
     -e 's/@ac_cv_have___builtin_expect@/1/g' \
     -e 's/@ac_cv_have_.*@/0/g' \
-    -e 's/@ac_google_start_namespace@/namespace google {/g' \
-    -e 's/@ac_google_end_namespace@/}/g' \
+    -e 's/@ac_google_start_namespace@/namespace google {{/g' \
+    -e 's/@ac_google_end_namespace@/}}/g' \
     -e 's/@ac_google_namespace@/google/g' \
     -e 's/@ac_cv___attribute___noinline@/__attribute__((noinline))/g' \
     -e 's/@ac_cv___attribute___noreturn@/__attribute__((noreturn))/g' \
     -e 's/@ac_cv___attribute___printf_4_5@/__attribute__((__format__ (__printf__, 4, 5)))/g'
 EOF
-''',
+'''.format(int(with_gflags)),
     )
 
     native.genrule(