libbacktrace: Reapply Rust-specific changes

New: Fix for rust-lang#28447 Merged: openbsd support: rust-lang@fcb30a0 bitrig integration: rust-lang@cd8f317 Not merged: rust-lang@d4fc3ec @Diggsey says this change was unintended (rust-lang#30666 (comment))

Author: petrochenkov

src/libbacktrace/configure

@@ -5691,7 +5691,7 @@ else
  lt_cv_sys_max_cmd_len=8192;
  ;;
 
- netbsd* | freebsd* | openbsd* | darwin* | dragonfly*)
+ netbsd* | freebsd* | openbsd* | darwin* | dragonfly* | bitrig*)
  # This has been around since 386BSD, at least. Likely further.
  if test -x /sbin/sysctl; then
  lt_cv_sys_max_cmd_len=`/sbin/sysctl -n kern.argmax`
@@ -9374,7 +9374,7 @@ if test -z "$aix_libpath"; then aix_libpath="/usr/lib:/lib"; fi
  ;;
 
  # FreeBSD 3 and greater uses gcc -shared to do shared libraries.
- freebsd* | dragonfly*)
+ freebsd* | dragonfly* | openbsd* | bitrig*)
  archive_cmds='$CC -shared -o $lib $libobjs $deplibs $compiler_flags'
  hardcode_libdir_flag_spec='-R$libdir'
  hardcode_direct=yes

src/libbacktrace/ltmain.sh

@@ -4741,7 +4741,7 @@ func_mode_link ()
  # These systems don't actually have a C library (as such)
  test "X$arg" = "X-lc" && continue
  ;;
- *-*-openbsd* | *-*-freebsd* | *-*-dragonfly*)
+ *-*-openbsd* | *-*-freebsd* | *-*-dragonfly* | *-*-bitrig*)
  # Do not include libc due to us having libc/libc_r.
  test "X$arg" = "X-lc" && continue
  ;;

src/libbacktrace/pecoff.c

@@ -602,7 +602,7 @@ coff_add (struct backtrace_state *state, int descriptor,
  const b_coff_section_header *sects;
  struct backtrace_view str_view;
  int str_view_valid;
- size_t str_size;
+ uint32_t str_size;
  off_t str_off;
  struct backtrace_view syms_view;
  off_t syms_off;