Properly check valgrind arches

Signed-off-by: David Abdurachmanov <davidlt@rivosinc.com>

libinsane.spec

@@ -1,6 +1,6 @@
 Name:           libinsane
 Version:        1.0.10
-Release:        %autorelease
+Release:        %autorelease -e 0.riscv64
 Summary:        Cross-platform access to image scanners
 
 License:        LGPL-3.0-or-later
@@ -15,7 +15,9 @@ BuildRequires:  gcc
 BuildRequires:  pkgconfig(sane-backends)
 BuildRequires:  doxygen
 BuildRequires:  pkgconfig(cunit)
+%ifarch %{valgrind_arches}
 BuildRequires:  valgrind
+%endif
 
 %description
 Libinsane is the library to access scanners on both Linux and Windows. It's