gcc-runtime: Disable gcc version of libssp

libssp is implemented fully in glibc as well as in musl so we really do not need the gcc version of this library except may be for mingw, where we keep it enabled anyway gcc in OE is built with the knowledge that C library already provides libssp implementation, we should therefore not need the gcc implementation of same.

libssp_nonshared piece is a detail which is needed when gcc is the compiler, in glibc this is part of libc_nonshared.a already and libc_nonshared.a is linked always when linking with -lc becuase libc.so in glibc is actually a linker script

GROUP ( /usr/lib/libc.so.6 /usr/lib/libc_nonshared.a AS_NEEDED ( /usr/lib/ld-linux-x86-64.so.2 ) )

which automatically links in the needed runtime bits, this however is not the case for musl, where core SSP APIs are implemented in full but compiler specific runtime isn't, for this we add a new package called libssp_nonshared which generate the needed runtime stub and gcc is already carrying patch to link to libssp_nonshared.a on musl

This should fix a long standing problem where static PIE executable were not buildable with OE since it was conflicting SSP implementation one from C library and the other one from gcc and we end up with duplicate symbol errors during linking.

Backport a patch from trunk which enhances enable|disable-libssp to not only disable building libssp but also not emit the gcc specs to use it for subsequent linking when stack-protector options are used on compiler cmdline

---
Changes since v1:
- Backport a patch to enhance semantics of enable|disable-libssp
- Pass SSP option to gcc initial recipes as well

 meta/recipes-devtools/gcc/gcc-7.3.inc         |   7 +-
 ...cc-override-TARGET_LIBC_PROVIDES_SSP.patch | 204 ++++++++++++++++++
 meta/recipes-devtools/gcc/gcc-runtime.inc     |   4 +-
 3 files changed, 212 insertions(+), 3 deletions(-)
 create mode 100644 meta/recipes-devtools/gcc/gcc-7.3/0049-gcc-override-TARGET_LIBC_PROVIDES_SSP.patch

index d968c322d2..98e5383b3c 100644
@@ -72,6 +72,7 @@ SRC_URI = "\
            file://0045-Link-libgcc-using-LDFLAGS-not-just-SHLIB_LDFLAGS.patch \
            file://0047-sync-gcc-stddef.h-with-musl.patch \
            file://0048-gcc-Enable-static-PIE.patch \
+           file://0049-gcc-override-TARGET_LIBC_PROVIDES_SSP.patch \
            file://fix-segmentation-fault-precompiled-hdr.patch \
            file://no-sse-fix-test-case-failures.patch \
            ${BACKPORTS} \

@@ -93,10 +94,12 @@ FORTRAN = ""
 JAVA = ""
 
 LTO = "--enable-lto"
+SSP ?= "--disable-libssp"
+SSP_mingw = "--enable-libssp"
 
 EXTRA_OECONF_BASE = "\
     ${LTO} \
-    --enable-libssp \
+    ${SSP} \
     --enable-libitm \
     --disable-bootstrap \
     --disable-libmudflap \

@@ -120,7 +123,7 @@ EXTRA_OECONF_INITIAL = "\
     --disable-plugin \
     --enable-decimal-float=no \
     --without-isl \
-    gcc_cv_libc_provides_ssp=yes \
+    ${SSP} \
 "
 
 EXTRA_OECONF_PATHS = "\

index 97365a21dc..b4e5539575 100644
@@ -24,8 +24,10 @@ RUNTIMELIBITM_nios2 = ""
 RUNTIMELIBITM_microblaze = ""
 RUNTIMELIBITM_riscv32 = ""
 RUNTIMELIBITM_riscv64 = ""
+RUNTIMELIBSSP ?= ""
+RUNTIMELIBSSP_mingw ?= "libssp"
 
-RUNTIMETARGET = "libssp libstdc++-v3 libgomp libatomic ${RUNTIMELIBITM} \
+RUNTIMETARGET = "libstdc++-v3 libgomp libatomic ${RUNTIMELIBITM} \
     ${@bb.utils.contains_any('FORTRAN', [',fortran',',f77'], 'libquadmath', '', d)} \
 "
 RUNTIMETARGET_append_x86 = " libmpx"

2.17.0