bugfix: we removed the existing Makefile even for `./configure --help`.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

t/sanity.t

@@ -1327,8 +1327,8 @@ install: all
 clean:
 	rm -rf build
 --- err
-Can't exec "gcc-4.2": No such file or directory at ./configure line 625.
+Can't exec "gcc-4.2": No such file or directory at ./configure line 621.
-Can't exec "gcc-4.2": No such file or directory at ./configure line 663.
+Can't exec "gcc-4.2": No such file or directory at ./configure line 659.
 
 
 
@@ -1498,8 +1498,8 @@ install: all
 clean:
 	rm -rf build
 --- err
-Can't exec "cl": No such file or directory at ./configure line 625.
+Can't exec "cl": No such file or directory at ./configure line 621.
-Can't exec "cl": No such file or directory at ./configure line 663.
+Can't exec "cl": No such file or directory at ./configure line 659.
 
 
 
@@ -1700,7 +1700,7 @@ clean:
 
 --- err
 --with-libpq is not allowed when --with-pg_config is already specified.
---- exit: 2
+--- exit: 255
 
 
 
@@ -2297,7 +2297,7 @@ install: all
 clean:
 	rm -rf build
 --- err
-Can't exec "sw_vers": No such file or directory at ./configure line 722.
+Can't exec "sw_vers": No such file or directory at ./configure line 718.
 
 
 
@@ -2382,7 +2382,7 @@ install: all
 clean:
 	rm -rf build
 --- err
-Can't exec "sw_vers": No such file or directory at ./configure line 722.
+Can't exec "sw_vers": No such file or directory at ./configure line 718.
 
 
 

util/configure

@@ -23,10 +23,6 @@ my $OS = $^O;
 
 my $ngx_dir;
 
-if (-f 'Makefile') {
-    unlink 'Makefile' or die "ERROR: failed to remove existing Makefile: $!\n";
-}
-
 for my $opt (@ARGV) {
     if ($opt =~ /^--platform=(.*)/) {
         $OS = $1;
@@ -1368,6 +1364,11 @@ _EOC_
 }
 
 sub gen_makefile {
+    if (-f 'Makefile') {
+        unlink 'Makefile' or
+            die "ERROR: failed to remove existing Makefile: $!\n";
+    }
+
     open my $out, ">Makefile" or
         die "Cannot open Makefile for writing: $!\n";