[RFC] pcc support for configure

[Isaac Dunham <idunham@lavabit.com>]

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Now that pcc can build a working libc.so*, I thought I'd try adding pcc to the configure script.
I don't anticipate these changes to be the final version; feel free to suggest improvements.
-m* is tested for link success with this patch; this fixes the "Unrecognized emulation mode" when using pcc, while letting gcc add the 
-m* options.

*Note: pcc can be built with binutils (default) or yasm (--with-yasm). Apparently yasm is missing quite a few instructions, as even when I used yasm from git I got a quite spectacular FTBFS using pcc+yasm as compiler.
Only pcc with binutils is supported.
Also, pcc-libs must be built with -fPIC.
HTH,
Isaac Dunham <idunham@lavabit.com>

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diff --git a/configure b/configure
index 9b06d2b..828b156 100755
--- a/configure
+++ b/configure
@@ -162,6 +162,7 @@ printf "checking for C compiler... "
 trycc ${CROSS_COMPILE}gcc
 trycc ${CROSS_COMPILE}c99
 trycc ${CROSS_COMPILE}cc
+trycc ${CROSS_COMPILE}pcc
 printf "%s\n" "$CC"
 test -n "$CC" || { echo "$0: cannot find a C compiler" ; exit 1 ; }
 
@@ -219,6 +220,14 @@ tryflag CFLAGS_C99FSE -fexcess-precision=standard \
 tryflag CFLAGS_C99FSE -frounding-math
 
 #
+# Older PCC versions don't define __PIC__ with -fPIC
+#
+tryflag CFLAG_TEST "-x c"
+printf '#ifndef __PIC__\n__PIC__=0\n#endif\n' | \
+$CC -E $CFLAG_TEST -fPIC - | grep __PIC__ && \
+CFLAGS_SHARED_ALL="$CFLAGS_SHARED_ALL -D__PIC__=1"
+
+#
 # Setup basic default CFLAGS: debug, optimization, and -pipe
 #
 if fnmatch '-O*|*\ -O*' "$CFLAGS_AUTO $CFLAGS" ; then :
@@ -269,8 +278,8 @@ tryflag CFLAGS_AUTO -falign-jumps=1
 # work anyway (issues with atomic ops).
 #
 if test "$ARCH" = "i386" ; then
-fnmatch '-march=*|*\ -march=*' "$CFLAGS" || tryflag CFLAGS_AUTO -march=i486
-fnmatch '-mtune=*|*\ -mtune=*' "$CFLAGS" || tryflag CFLAGS_AUTO -mtune=generic
+fnmatch '-march=*|*\ -march=*' "$CFLAGS" || tryldflag CFLAGS_AUTO -march=i486
+fnmatch '-mtune=*|*\ -mtune=*' "$CFLAGS" || tryldflag CFLAGS_AUTO -mtune=generic
 fi
 
 if test "x$warnings" = xyes ; then
@@ -299,6 +308,7 @@ shared=no
 # Find compiler runtime library
 test -z "$LIBCC" && tryldflag LIBCC -lgcc && tryldflag LIBCC -lgcc_eh
 test -z "$LIBCC" && tryldflag LIBCC -lcompiler_rt
+test -z "$LIBCC" && tryldflag LIBCC `$CC -print-file-name=libpcc.a || true`
 printf "using compiler runtime libraries: %s\n" "$LIBCC"
 
 
@@ -325,6 +335,7 @@ LDFLAGS = $LDFLAGS_AUTO $LDFLAGS
 CROSS_COMPILE = $CROSS_COMPILE
 LIBCC = $LIBCC
 EOF
+test "x$CFLAGS_ALL_SHARED" != x && echo "CFLAGS_ALL_SHARED += $CFLAGS_ALL_SHARED"
 test "x$static" = xno && echo "STATIC_LIBS ="
 test "x$shared" = xno && echo "SHARED_LIBS ="
 test "x$wrapper" = xno && echo "ALL_TOOLS ="