Ignore RPM environment variables (#1613)

RPM sets a number of environment variables by default that interfere
with the sccache's ability to cache artefacts. Some of these
variables are also used by other applications.

This extends the default ignore list to allow sccache to be used
under different environments for caching.

src/cmdline.rs

@@ -278,7 +278,19 @@ pub fn try_parse() -> Result<Command> {
                 //
                 // FIXME: Maybe we should strip out `LD_PRELOAD` always?
                 if env::var_os("RUNNING_UNDER_RR").is_some() {
-                    env_vars.retain(|(k, _v)| k != "LD_PRELOAD" && k != "RUNNING_UNDER_RR");
+                    env_vars.retain(|(k, _v)| {
+                        k != "LD_PRELOAD"
+                            && k != "RUNNING_UNDER_RR"
+                            && k != "HOSTNAME"
+                            && k != "PWD"
+                            && k != "HOST"
+                            && k != "RPM_BUILD_ROOT"
+                            && k != "SOURCE_DATE_EPOCH"
+                            && k != "RPM_PACKAGE_RELEASE"
+                            && k != "MINICOM"
+                            && k != "DESTDIR"
+                            && k != "RPM_PACKAGE_VERSION"
+                    });
                 }
 
                 let cmd = matches