Set RUSTC_BOOTSTRAP=1 consistently unless manually configured

Signed-off-by: onur-ozkan <work@onurozkan.dev>

src/bootstrap/bootstrap.py

@@ -924,11 +924,14 @@ def build_bootstrap_cmd(self, env):
         # default toolchain is not nightly.
         #
         # But that setting has the collateral effect of rust-analyzer also
-        # passing RUSTC_BOOTSTRAP=1 to all x.py invocations too (the various
-        # overrideCommand). For compiling bootstrap, that is unwanted and can
-        # cause spurious rebuilding of bootstrap when rust-analyzer x.py
-        # invocations are interleaved with handwritten ones on the command line.
-        env.pop("RUSTC_BOOTSTRAP", None)
+        # passing RUSTC_BOOTSTRAP=1 to all x.py invocations too (the various overrideCommand).
+        # For compiling bootstrap that can cause spurious rebuilding of bootstrap when
+        # rust-analyzer x.py invocations are interleaved with handwritten ones on the
+        # command line.
+        #
+        # Set RUSTC_BOOTSTRAP=1 consistently unless manually configured.
+        if 'RUSTC_BOOTSTRAP' not in env:
+            env['RUSTC_BOOTSTRAP'] = '1'
 
         # preserve existing RUSTFLAGS
         env.setdefault("RUSTFLAGS", "")