lang/gcc15: Add port

GCC, the GNU Compiler Collection, supports a number of languages.
This port installs the C, C++, and Fortran front ends as gcc15,
g++15, and gfortran15, respectively.

This is the first release from the GCC 15 series.
It largely is a copy of lang/gcc15-devel, with release-specific
modifications from lang/gcc14.

Common issues that could happen when porting code to GCC 15:
https://gcc.gnu.org/gcc-15/porting_to.html

Changes: https://gcc.gnu.org/gcc-15/changes.html

Note: files/patch-libgcc_unwind.inc will get obsolete once all supported
FreeBSD releases include commit
22e564c74eb20e14bd93fd9fdde20e38a29cfcf1. [1]

PR:             285711 [1]

1 files changed, 18 insertions, 0 deletions

diff --git a/lang/gcc15/files/patch-libcxxrt b/lang/gcc15/files/patch-libcxxrt
new file mode 100644
index 000000000000..4225df7aad1e
--- /dev/null
+++ b/lang/gcc15/files/patch-libcxxrt
@@ -0,0 +1,18 @@
+libc++ on FreeBSD always uses PathScale libcxxrt and cannot change to
+LLVM libc++abi without breaking backward compatibility. Besides, mixing
+different C++ ABIs is not supported unless subset via DT_FILTER.
+
+https://github.com/llvm/llvm-project/commit/35479ffb1251
+https://github.com/freebsd/freebsd-src/commit/cf56074e5271
+
+--- gcc/cp/g++spec.cc.orig	2022-07-31 22:32:16 UTC
++++ gcc/cp/g++spec.cc
+@@ -60,7 +60,7 @@ along with GCC; see the file COPYING3.  If not see
+ #endif
+ 
+ #ifndef LIBCXXABI
+-#define LIBCXXABI "c++abi"
++#define LIBCXXABI "cxxrt"
+ #endif
+ #ifndef LIBCXXABI_PROFILE
+ #define LIBCXXABI_PROFILE LIBCXXABI