Turn valgrind bcond into in-place %ifarch

There's no way to turn this bcond off on arches where it is not supported.
There's no need to turn this bcond on on arches where it is supported.

python3.13.spec

@@ -135,14 +135,6 @@ Provides: bundled(python3dist(packaging)) = 24
 # Main interpreter loop optimization
 %bcond computed_gotos 1
 
-# Support for the Valgrind debugger/profiler
-# (no way to use %%ifarch as an expression)
-%ifarch %{valgrind_arches}
-%bcond valgrind 1
-%else
-%bcond valgrind 0
-%endif
-
 # =====================
 # General global macros
 # =====================
@@ -295,7 +287,7 @@ BuildRequires: clang(major) = 18
 BuildRequires: llvm(major) = 18
 %endif
 
-%if %{with valgrind}
+%ifarch %{valgrind_arches}
 BuildRequires: valgrind-devel
 %endif
 
@@ -877,7 +869,7 @@ BuildPython() {
 %if %{with rpmwheels}
   --with-wheel-pkg-dir=%{python_wheel_dir} \
 %endif
-%if %{with valgrind}
+%ifarch %{valgrind_arches}
   --with-valgrind \
 %endif
   $ExtraConfigArgs \