gcc: update to version 7.4.0, Add config options

for coping libc.a, libpthread.a and libstdc++ to target.
Add config option to eliminate need for -lstdc++ and -lgcc_pic
switches when linking statically

Signed-off-by: Noble Pepper <noblepepper@gmail.com>

devel/gcc/patches/230-musl_libssp.patch

@@ -1,6 +1,21 @@
+commit 1877bc9d8f2be143fbe530347a945850d0ecd234
+Author: Steven Barth <cyrus@openwrt.org>
+Date:   Mon Jun 22 10:31:07 2015 +0000
+
+    gcc/musl: rework SSP-support
+    
+    Make musl provide libssp_nonshared.a and make GCC link it unconditionally
+    if musl is used. This should be a no-op if SSP is disabled and seems to be
+    the only reliable way of dealing with SSP over all packages due to the mess
+    that is linkerflags handling in packages.
+    
+    Signed-off-by: Steven Barth <steven@midlink.org>
+    
+    SVN-Revision: 46108
+
 --- a/gcc/gcc.c
 +++ b/gcc/gcc.c
-@@ -727,7 +727,9 @@ proper position among the other output f
+@@ -861,7 +861,9 @@ proper position among the other output f
  #endif
  
  #ifndef LINK_SSP_SPEC