tpl: Workaround s390x precision of Atan and Tan

On s390x, math.Atan(1) and math.Tan(1) give values that slightly differ
from other architectures, causing TestTemplateFuncsExamples to fail.

The golang math package states in the overview:
"This package does not guarantee bit-identical results across architectures."

tpl/math/init.go

@@ -15,6 +15,7 @@ package math
 
 import (
 	"context"
+	"runtime"
 
 	"github.com/gohugoio/hugo/deps"
 	"github.com/gohugoio/hugo/tpl/internal"
@@ -23,6 +24,13 @@ import (
 const name = "math"
 
 func init() {
+	mathAtan1 := "0.7853981633974483"
+	mathTan1 := "1.557407724654902"
+	if runtime.GOARCH == "s390x" {
+		mathAtan1 = "0.7853981633974484"
+		mathTan1 = "1.5574077246549018"
+	}
+
 	f := func(d *deps.Deps) *internal.TemplateFuncsNamespace {
 		ctx := New(d)
 
@@ -62,7 +70,7 @@ func init() {
 		ns.AddMethodMapping(ctx.Atan,
 			nil,
 			[][2]string{
-				{"{{ math.Atan 1 }}", "0.7853981633974483"},
+				{"{{ math.Atan 1 }}", mathAtan1},
 			},
 		)
 
@@ -202,7 +210,7 @@ func init() {
 		ns.AddMethodMapping(ctx.Tan,
 			nil,
 			[][2]string{
-				{"{{ math.Tan 1 }}", "1.557407724654902"},
+				{"{{ math.Tan 1 }}", mathTan1},
 			},
 		)