Fix LazyString building with non-ASCII preceding $ (#49248)

(cherry picked from commit bd1a664)

Author: Liozou

base/strings/lazy.jl

@@ -67,7 +67,7 @@ macro lazy_str(text)
     parts = Any[]
     lastidx = idx = 1
     while (idx = findnext('$', text, idx)) !== nothing
-        lastidx < idx && push!(parts, text[lastidx:idx-1])
+        lastidx < idx && push!(parts, text[lastidx:prevind(text, idx)])
         idx += 1
         expr, idx = Meta.parseatom(text, idx; filename=string(__source__.file))
         push!(parts, esc(expr))

test/strings/basic.jl

@@ -1144,4 +1144,7 @@ end
         end
         return a
     end |> Core.Compiler.is_foldable
+    let i=49248
+        @test String(lazy"PR n°$i") == "PR n°49248"
+    end
 end