Solaris build needs -std=gnu89

[Jesse Off]

Solaris build fails with:

//setting up OS-dependent information
make: Entering directory `/u/home/joff/sbcl/tools-for-build'
gcc -m64 -g -O2 -Wall -D__EXTENSIONS__ -D_POSIX_C_SOURCE=199506L -DSVR4 -D_REENTRANT -fno-omit-frame-pointer -I../src/runtime determine-endianness.c -ldl -lsocket -lnsl -lrt -o determine-endianness
In file included from /opt/csw/lib/gcc/i386-pc-solaris2.10/5.5.0/include-fixed/stdio.h:30:0,
                 from determine-endianness.c:20:
/opt/csw/lib/gcc/i386-pc-solaris2.10/5.5.0/include-fixed/sys/feature_tests.h:346:2: error: #error "Compiler or options invalid for pre-UNIX 03 X/Open applications and pre-2001 POSIX applications"
 #error "Compiler or options invalid for pre-UNIX 03 X/Open applications \
  ^
make: *** [determine-endianness] Error 1
make: Leaving directory `/u/home/joff/sbcl/tools-for-build'

Fix:
diff --git a/src/runtime/Config.x86-64-sunos b/src/runtime/Config.x86-64-sunos
index 17eef04..e709909 100644
--- a/src/runtime/Config.x86-64-sunos
+++ b/src/runtime/Config.x86-64-sunos
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS = -m64 -g -O2 -Wall -D__EXTENSIONS__ -D_POSIX_C_SOURCE=199506L -DSVR4 -D_REENTRANT -fno-omit-frame-pointer
+CFLAGS = -m64 -g -O2 -Wall -std=gnu89 -D__EXTENSIONS__ -D_POSIX_C_SOURCE=199506L -DSVR4 -D_REENTRANT -fno-omit-frame-pointer
 LINKFLAGS = -m64 -g
 ASFLAGS = -m64 -Wall
 NM = nm -xgp

[Douglas Katzman (dougk)]

done
https://sourceforge.net/p/sbcl/sbcl/ci/7f952dc62ef758328478d3a817cf4dff9e2e3ee4