Add C++2z-trivial-relocation branch

From the request:

Trivial relocation was landed in GCC 16 and then withdrawn because it
was pulled from the C++ Working Draft. This branch maintains the current
work on trivial relocation, including fixes that have been made since it
was removed from the WD.

Refs compiler-explorer/compiler-explorer#8337

Signed-off-by: Marc Poulhiès <dkm@kataplop.net>

Author: dkm

build/build.sh

@@ -140,6 +140,13 @@ elif echo "${VERSION}" | grep 'contracts-GNUext-trunk'; then
     MAJOR=16
     MAJOR_MINOR=16-trunk
     LANGUAGES=c++
+elif echo "${VERSION}" | grep 'trivial-relocation-trunk'; then
+    VERSION=contracts-GNUext-trunk-$(date +%Y%m%d)
+    URL=git@github.com:iains/gcc-git.git
+    BRANCH="C++2z-trivial-relocation"
+    MAJOR=16
+    MAJOR_MINOR=16-trunk
+    LANGUAGES=c++
 elif echo "${VERSION}" | grep 'thomas-healy-trunk'; then
     VERSION=thomas-healy-trunk-$(date +%Y%m%d)
     URL=https://github.com/healytpk/gcc-thomas-healy.git