[pushed: r15-4739] jit: fix leak of pending_assemble_externals_set [PR117275]

[David Malcolm]

My recent r15-4580-g779c0390e3b57d fix for resetting state in
varasm.cc introduced some noise to "make selftest-valgrind" and,
presumably, a memory leak in libgccjit:

==2462086== 160 (56 direct, 104 indirect) bytes in 1 blocks are definitely lost 
in loss record 248 of 352
==2462086==    at 0x5270E7D: operator new(unsigned long) 
(vg_replace_malloc.c:342)
==2462086==    by 0x1D1EB89: init_varasm_once() (varasm.cc:6806)
==2462086==    by 0x181C845: backend_init() (toplev.cc:1826)
==2462086==    by 0x181D41A: do_compile() (toplev.cc:2193)
==2462086==    by 0x181D99C: toplev::main(int, char**) (toplev.cc:2371)
==2462086==    by 0x378391D: main (main.cc:39)

Fixed thusly.

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Tested lightly on powerpc64le-unknown-linux-gnu.
Pushed to trunk as r15-4739-g7f41203f08b994.

gcc/ChangeLog:
        PR jit/117275
        * varasm.cc (process_pending_assemble_externals): Reset
        pending_assemble_externals_set to nullptr after deleting it.
        (varasm_cc_finalize): Delete pending_assemble_externals_set.

Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
 gcc/varasm.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/varasm.cc b/gcc/varasm.cc
index ce1077b6d4bd..deefbac5b7b2 100644
--- a/gcc/varasm.cc
+++ b/gcc/varasm.cc
@@ -2575,6 +2575,7 @@ process_pending_assemble_externals (void)
   pending_assemble_externals_processed = true;
   pending_libcall_symbols = NULL_RTX;
   delete pending_assemble_externals_set;
+  pending_assemble_externals_set = nullptr;
 #endif
 }
 
@@ -8893,6 +8894,7 @@ varasm_cc_finalize ()
 
 #ifdef ASM_OUTPUT_EXTERNAL
   pending_assemble_externals_processed = false;
+  delete pending_assemble_externals_set;
   pending_assemble_externals_set = nullptr;
 #endif
 
-- 
2.26.3