rustbuild: Don't enable debuginfo in rustc

In #37280 we enabled line number debugging information in release artifacts,
primarily to close out #36452 where debugging information was critical for MSVC
builds of Rust to be useful in production. This commit, however, apparently had
some unfortunate side effects.

Namely it was noticed in #37477 that if `RUST_BACKTRACE=1` was set then any
compiler error would take a very long time for the compiler to exit. The cause
of the problem here was somewhat deep:

* For all compiler errors, the compiler will `panic!` with a known value. This
  tears down the main compiler thread and allows cleaning up all the various
  resources. By default, however, this panic output is suppressed for "normal"
  compiler errors.
* When `RUST_BACKTRACE=1` was set this caused every compiler error to generate a
  backtrace.
* The libbacktrace library hits a pathological case where it spends a very long
  time in its custom allocation function, `backtrace_alloc`, because the
  compiler has so much debugging information. More information about this can be
  found in #29293 with a summary at the end of #37477.

To solve this problem this commit simply removes debuginfo from the compiler but
not from the standard library. This should allow us to keep #36452 closed while
also closing #37477. I've measured the difference to be orders of magnitude
faster than it was before, so we should see a much quicker time-to-exit after a
compile error when `RUST_BACKTRACE=1` is set.

Closes #37477
Closes #37571

1 files changed, 9 insertions, 4 deletions

diff --git a/configure b/configure
index ee5922b1f14..a93a6c5a3a6 100755
--- a/configure
+++ b/configure
@@ -647,6 +647,7 @@ opt_nosave debug-assertions 0 "build with debugging assertions"
 opt_nosave llvm-release-debuginfo 0 "build LLVM with debugger metadata"
 opt_nosave debuginfo 0 "build with debugger metadata"
 opt_nosave debuginfo-lines 0 "build with line number debugger metadata"
+opt_nosave debuginfo-only-std 0 "build only libstd with debugging information"
 opt_nosave debug-jemalloc 0 "build jemalloc with --enable-debug --enable-fill"
 
 valopt localstatedir "/var/lib" "local state directory"
@@ -733,15 +734,17 @@ case "$CFG_RELEASE_CHANNEL" in
     nightly )
 	msg "overriding settings for $CFG_RELEASE_CHANNEL"
 	CFG_ENABLE_LLVM_ASSERTIONS=1
-
-        # FIXME(#37364) shouldn't have to disable this on windows-gnu
+        # FIXME(stage0) re-enable this on the next stage0 now that #35566 is
+        # fixed
         case "$CFG_BUILD" in
           *-pc-windows-gnu)
             ;;
           *)
-	    CFG_ENABLE_DEBUGINFO_LINES=1
+            CFG_ENABLE_DEBUGINFO_LINES=1
+            CFG_ENABLE_DEBUGINFO_ONLY_STD=1
             ;;
         esac
+
 	;;
     beta | stable)
 	msg "overriding settings for $CFG_RELEASE_CHANNEL"
@@ -749,7 +752,8 @@ case "$CFG_RELEASE_CHANNEL" in
           *-pc-windows-gnu)
             ;;
           *)
-	    CFG_ENABLE_DEBUGINFO_LINES=1
+            CFG_ENABLE_DEBUGINFO_LINES=1
+            CFG_ENABLE_DEBUGINFO_ONLY_STD=1
             ;;
         esac
 	;;
@@ -785,6 +789,7 @@ if [ -n "$CFG_ENABLE_DEBUG_ASSERTIONS" ]; then putvar CFG_ENABLE_DEBUG_ASSERTION
 if [ -n "$CFG_ENABLE_LLVM_RELEASE_DEBUGINFO" ]; then putvar CFG_ENABLE_LLVM_RELEASE_DEBUGINFO; fi
 if [ -n "$CFG_ENABLE_DEBUGINFO" ]; then putvar CFG_ENABLE_DEBUGINFO; fi
 if [ -n "$CFG_ENABLE_DEBUGINFO_LINES" ]; then putvar CFG_ENABLE_DEBUGINFO_LINES; fi
+if [ -n "$CFG_ENABLE_DEBUGINFO_ONLY_STD" ]; then putvar CFG_ENABLE_DEBUGINFO_ONLY_STD; fi
 if [ -n "$CFG_ENABLE_DEBUG_JEMALLOC" ]; then putvar CFG_ENABLE_DEBUG_JEMALLOC; fi
 
 step_msg "looking for build programs"