Don't hardcode usr/share/rpm

We don't need this on modern Fedora anymore for example.
If we detect the sysimage path, then just use it.

src/ostreeutil.rs

@@ -6,20 +6,24 @@
 
 use std::path::Path;
 
+use anyhow::Result;
+
 /// https://github.com/coreos/rpm-ostree/pull/969/commits/dc0e8db5bd92e1f478a0763d1a02b48e57022b59
 #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
 pub(crate) const BOOT_PREFIX: &str = "usr/lib/ostree-boot";
+const LEGACY_RPMOSTREE_DBPATH: &str = "usr/share/rpm";
+const SYSIMAGE_RPM_DBPATH: &str = "usr/lib/sysimage/rpm";
 
-pub(crate) fn rpm_cmd<P: AsRef<Path>>(sysroot: P) -> std::process::Command {
+pub(crate) fn rpm_cmd<P: AsRef<Path>>(sysroot: P) -> Result<std::process::Command> {
+    let mut c = std::process::Command::new("rpm");
     let sysroot = sysroot.as_ref();
-    let dbpath = sysroot.join("usr/share/rpm");
-    let dbpath_arg = {
+    let modern_dbpath = sysroot.join(SYSIMAGE_RPM_DBPATH);
+    if !modern_dbpath.try_exists()? {
+        let dbpath = sysroot.join(LEGACY_RPMOSTREE_DBPATH);
         let mut s = std::ffi::OsString::new();
         s.push("--dbpath=");
         s.push(dbpath.as_os_str());
-        s
+        c.arg(s);
     };
-    let mut c = std::process::Command::new("rpm");
-    c.arg(&dbpath_arg);
-    c
+    Ok(c)
 }

src/packagesystem.rs

@@ -52,7 +52,7 @@ pub(crate) fn query_files<T>(
 where
     T: AsRef<Path>,
 {
-    let mut c = ostreeutil::rpm_cmd(sysroot_path);
+    let mut c = ostreeutil::rpm_cmd(sysroot_path)?;
     c.args(["-q", "--queryformat", "%{nevra},%{buildtime} ", "-f"]);
     for arg in paths {
         c.arg(arg.as_ref());