Have ./configure use the compiler return code for error indication.

Previously ./configure would use any output on stderr as an indication
that the compilation failed.  However if some compiler wrapper uses
stderr for some other purpose, e.g. distcc for nodes going down, then
./configure would not properly configure the build.  This problem was
noted by Mike Frysinger.  For backwards compatibility, ./configure
will revert to the old way, i.e. checking for anything on stderr, if
when it deliberately runs the compiler with an error, a zero exit
status is returned.

configure

@@ -97,6 +97,22 @@ case "$1" in
 done
 
 test=ztest$$
+
+cat > $test.c <<EOF
+#error error
+EOF
+if ($CC -c $CFLAGS $test.c) 2>/dev/null; then
+  try()
+  {
+    test "`( $* ) 2>&1`" = ""
+  }
+else
+  try()
+  {
+    ( $* ) 2>/dev/null
+  }
+fi
+
 cat > $test.c <<EOF
 extern int getchar();
 int hello() {return getchar();}
@@ -249,8 +265,8 @@ SHAREDLIBM=${SHAREDLIBM-"libz$shared_ext.$VER1"}
 if test $shared -eq 1; then
   echo Checking for shared library support...
   # we must test in two steps (cc then ld), required at least on SunOS 4.x
-  if test "`($CC -w -c $SFLAGS $test.c) 2>&1`" = "" &&
-     test "`($LDSHARED $SFLAGS -o $test$shared_ext $test.o) 2>&1`" = ""; then
+  if try $CC -w -c $SFLAGS $test.c &&
+     try $LDSHARED $SFLAGS -o $test$shared_ext $test.o; then
     echo Building shared library $SHAREDLIBV with $CC.
   elif test -z "$old_cc" -a -z "$old_cflags"; then
     echo No shared library support.
@@ -281,7 +297,7 @@ cat > $test.c <<EOF
 #include <sys/types.h>
 off64_t dummy = 0;
 EOF
-if test "`($CC -c $CFLAGS -D_LARGEFILE64_SOURCE=1 $test.c) 2>&1`" = ""; then
+if try $CC -c $CFLAGS -D_LARGEFILE64_SOURCE=1 $test.c; then
   CFLAGS="${CFLAGS} -D_LARGEFILE64_SOURCE=1"
   SFLAGS="${SFLAGS} -D_LARGEFILE64_SOURCE=1"
   ALL="${ALL} all64"
@@ -297,7 +313,7 @@ int main(void) {
   return 0;
 }
 EOF
-  if test "`($CC $CFLAGS -o $test $test.c) 2>&1`" = ""; then
+  if try $CC $CFLAGS -o $test $test.c; then
     echo "Checking for fseeko... Yes."
   else
     CFLAGS="${CFLAGS} -DNO_FSEEKO"
@@ -312,7 +328,7 @@ cat > $test.c <<EOF
 #include <unistd.h>
 int main() { return 0; }
 EOF
-if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+if try $CC -c $CFLAGS $test.c; then
   sed < zconf.h "/^#ifdef HAVE_UNISTD_H.* may be/s/def HAVE_UNISTD_H\(.*\) may be/ 1\1 was/" > zconf.temp.h
   mv zconf.temp.h zconf.h
   echo "Checking for unistd.h... Yes."
@@ -324,7 +340,7 @@ cat > $test.c <<EOF
 #include <stdarg.h>
 int main() { return 0; }
 EOF
-if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+if try $CC -c $CFLAGS $test.c; then
   sed < zconf.h "/^#ifdef HAVE_STDARG_H.* may be/s/def HAVE_STDARG_H\(.*\) may be/ 1\1 was/" > zconf.temp.h
   mv zconf.temp.h zconf.h
   echo "Checking for stdarg.h... Yes."
@@ -367,7 +383,7 @@ int main()
 }
 EOF
 
-if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+if try $CC -c $CFLAGS $test.c; then
   echo "Checking whether to use vs[n]printf() or s[n]printf()... using vs[n]printf()."
 
   cat > $test.c <<EOF
@@ -390,7 +406,7 @@ int main()
   return (mytest("Hello%d\n", 1));
 }
 EOF
-  if test "`($CC $CFLAGS -o $test $test.c) 2>&1`" = ""; then
+  if try $CC $CFLAGS -o $test $test.c; then
     echo "Checking for vsnprintf() in stdio.h... Yes."
 
     cat >$test.c <<EOF
@@ -415,7 +431,7 @@ int main()
 }
 EOF
 
-    if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+    if try $CC -c $CFLAGS $test.c; then
       echo "Checking for return value of vsnprintf()... Yes."
     else
       CFLAGS="$CFLAGS -DHAS_vsnprintf_void"
@@ -455,7 +471,7 @@ int main()
 }
 EOF
 
-    if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+    if try $CC -c $CFLAGS $test.c; then
       echo "Checking for return value of vsprintf()... Yes."
     else
       CFLAGS="$CFLAGS -DHAS_vsprintf_void"
@@ -486,7 +502,7 @@ int main()
 }
 EOF
 
-  if test "`($CC $CFLAGS -o $test $test.c) 2>&1`" = ""; then
+  if try $CC $CFLAGS -o $test $test.c; then
     echo "Checking for snprintf() in stdio.h... Yes."
 
     cat >$test.c <<EOF
@@ -505,7 +521,7 @@ int main()
 }
 EOF
 
-    if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+    if try $CC -c $CFLAGS $test.c; then
       echo "Checking for return value of snprintf()... Yes."
     else
       CFLAGS="$CFLAGS -DHAS_snprintf_void"
@@ -539,7 +555,7 @@ int main()
 }
 EOF
 
-    if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+    if try $CC -c $CFLAGS $test.c; then
       echo "Checking for return value of sprintf()... Yes."
     else
       CFLAGS="$CFLAGS -DHAS_sprintf_void"
@@ -565,7 +581,7 @@ int main()
   return 0;
 }
 EOF
-  if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+  if try $CC -c $CFLAGS $test.c; then
     echo "Checking for attribute(visibility) support... Yes."
   else
     CFLAGS="$CFLAGS -DNO_VIZ"