We don't list dtrace in DEPENDS so we shouldn't be depending on this header. 
It may or may not exist from preivous builds though. To be determinstic, disable
sdt.h usage always. This avoids build failures if the header is removed after configure
but before libgcc is compiled for example.

RP 2012/8/7

Upstream-Status: Inappropriate [hack]

Index: git/gcc/configure
===================================================================
--- git.orig/gcc/configure	2012-08-07 21:18:42.319247701 +0000
+++ git/gcc/configure	2012-08-07 21:19:08.939247082 +0000
@@ -26758,12 +26758,12 @@
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking sys/sdt.h in the target C library" >&5
 $as_echo_n "checking sys/sdt.h in the target C library... " >&6; }
 have_sys_sdt_h=no
-if test -f $target_header_dir/sys/sdt.h; then
-  have_sys_sdt_h=yes
-
-$as_echo "#define HAVE_SYS_SDT_H 1" >>confdefs.h
-
-fi
+#if test -f $target_header_dir/sys/sdt.h; then
+#  have_sys_sdt_h=yes
+#
+#$as_echo "#define HAVE_SYS_SDT_H 1" >>confdefs.h
+#
+#fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_sys_sdt_h" >&5
 $as_echo "$have_sys_sdt_h" >&6; }