build-libssp: Stop building the real libssp from GCC

As mingw-w64 now provides these routines, we no longer need to build
the original library from GCC.

As building with -fstack-protector-strong still links with -lssp
(and -lssp_nonshared), we still need to provide libraries with these
names, but they can be empty dummy libraries.

build-libssp.sh

@@ -16,16 +16,8 @@
 
 set -e
 
-CFGUARD_CFLAGS="-mguard=cf"
-
 while [ $# -gt 0 ]; do
     case "$1" in
-    --enable-cfguard)
-        CFGUARD_CFLAGS="-mguard=cf"
-        ;;
-    --disable-cfguard)
-        CFGUARD_CFLAGS=
-        ;;
     *)
         PREFIX="$1"
         ;;
@@ -33,73 +25,21 @@ while [ $# -gt 0 ]; do
     shift
 done
 if [ -z "$PREFIX" ]; then
-    echo "$0 [--enable-cfguard|--disable-cfguard] dest"
+    echo "$0 dest"
     exit 1
 fi
 
-MAKE=make
-if command -v gmake >/dev/null; then
-    MAKE=gmake
-fi
-
 mkdir -p "$PREFIX"
 PREFIX="$(cd "$PREFIX" && pwd)"
 export PATH="$PREFIX/bin:$PATH"
 
-: ${CORES:=$(nproc 2>/dev/null)}
-: ${CORES:=$(sysctl -n hw.ncpu 2>/dev/null)}
-: ${CORES:=4}
 : ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64}}
 
-download() {
-    if command -v wget >/dev/null; then
-        if [ -n "$2" ]; then
-            wget -O "$2" "$1"
-        else
-            wget "$1"
-        fi
-    else
-        if [ -n "$2" ]; then
-            curl -L -o "$2" "$1"
-        else
-            curl -LO "$1"
-        fi
-    fi
-}
-
-if [ ! -d libssp ]; then
-    download 'https://gitlab.com/watched/gcc-mirror/gcc/-/archive/releases/gcc-7.3.0/gcc-releases-gcc-7.3.0.tar.bz2?path=libssp' libssp.tar.bz2
-    tar xf libssp.tar.bz2 --strip-components=1
-    rm -f libssp.tar.bz2
-fi
-
-cp libssp-Makefile libssp/Makefile
-
-cd libssp
-
-# gcc/libssp's configure script runs checks for flags that clang doesn't
-# implement. We actually just need to set a few HAVE defines and compile
-# the .c sources.
-cp config.h.in config.h
-for i in HAVE_FCNTL_H HAVE_INTTYPES_H HAVE_LIMITS_H HAVE_MALLOC_H \
-    HAVE_MEMMOVE HAVE_MEMORY_H HAVE_MEMPCPY HAVE_STDINT_H HAVE_STDIO_H \
-    HAVE_STDLIB_H HAVE_STRINGS_H HAVE_STRING_H HAVE_STRNCAT HAVE_STRNCPY \
-    HAVE_SYS_STAT_H HAVE_SYS_TYPES_H HAVE_UNISTD_H HAVE_USABLE_VSNPRINTF \
-    HAVE_HIDDEN_VISIBILITY; do
-    cat config.h | sed 's/^#undef '$i'$/#define '$i' 1/' > tmp
-    mv tmp config.h
-done
-cat ssp/ssp.h.in | sed 's/@ssp_have_usable_vsnprintf@/define/' > ssp/ssp.h
-
 for arch in $ARCHS; do
-    [ -z "$CLEAN" ] || rm -rf build-$arch
-    mkdir -p build-$arch
-    cd build-$arch
-    $MAKE -f ../Makefile -j$CORES CROSS=$arch-w64-mingw32- CFGUARD_CFLAGS="$CFGUARD_CFLAGS"
-    mkdir -p "$PREFIX/$arch-w64-mingw32/bin"
-    cp libssp.a "$PREFIX/$arch-w64-mingw32/lib"
-    cp libssp_nonshared.a "$PREFIX/$arch-w64-mingw32/lib"
-    cp libssp.dll.a "$PREFIX/$arch-w64-mingw32/lib"
-    cp libssp-0.dll "$PREFIX/$arch-w64-mingw32/bin"
-    cd ..
+    if [ ! -f $PREFIX/$arch-w64-mingw32/lib/libssp.a ]; then
+        # Create empty dummy archives, to avoid failing when the compiler
+        # driver adds "-lssp -lssh_nonshared" when linking.
+        llvm-ar rcs $PREFIX/$arch-w64-mingw32/lib/libssp.a
+        llvm-ar rcs $PREFIX/$arch-w64-mingw32/lib/libssp_nonshared.a
+    fi
 done