package_rpm.bbclass: do not set the OS dynamically when building rpms

Packages need to contain just one value for the os field, otherwise
rpm will refuse to install them if they don't match what is in
/etc/rpm/platform.

(From OE-Core rev: 580ba965f5f38f6718a83f690bbe23a63fbcd3dd)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/package_rpm.bbclass

@@ -692,7 +692,7 @@ python do_package_rpm () {
     pkgwritedir = d.expand('${PKGWRITEDIRRPM}/${PACKAGE_ARCH_EXTEND}')
     d.setVar('RPM_PKGWRITEDIR', pkgwritedir)
     bb.debug(1, 'PKGWRITEDIR: %s' % d.getVar('RPM_PKGWRITEDIR'))
-    pkgarch = d.expand('${PACKAGE_ARCH_EXTEND}${HOST_VENDOR}-${HOST_OS}')
+    pkgarch = d.expand('${PACKAGE_ARCH_EXTEND}${HOST_VENDOR}-linux')
     bb.utils.mkdirhier(pkgwritedir)
     os.chmod(pkgwritedir, 0o755)