target.hardware: whitelist HOME on Linux

This resovles errors when nextpnr-ice40 tries to create directories in
the rootfs.

See: YosysHQ/oss-cad-suite-build#75

software/glasgow/target/hardware.py

@@ -135,11 +135,17 @@ def execute(self, build_dir=None, *, debug=False):
         if build_dir is None:
             build_dir = tempfile.mkdtemp(prefix="glasgow_")
         try:
-            environ = self.toolchain.env_vars
-            if os.name == 'nt':
+            env_whitelist = []
+
+            if os.name == "posix":
+                env_whitelist.append("HOME")
+            elif os.name == "nt":
                 # PROCESSOR_ARCHITECTURE: required for YoWASP (used by wasmtime)
-                for var in ("PROCESSOR_ARCHITECTURE",):
-                    environ[var] = os.environ[var]
+                env_whitelist.append("PROCESSOR_ARCHITECTURE")
+
+            environ = self.toolchain.env_vars
+            environ.update({ k:v for k,v in os.environ.items() if k in env_whitelist })
+
             products  = self.lower.execute_local(build_dir, env=environ)
             bitstream = products.get("top.bin")
         except: