git-branchless: enable PIC emitting on mips64el-like architectures

https://gcc.gnu.org/onlinedocs/gcc-14.1.0/gcc/Code-Gen-Options.html#index-fPIC

Author: KexyBiscuit

app-utils/git-branchless/autobuild/prepare

@@ -0,0 +1,14 @@
+# FIXME: not sure why is this required
+# The linker tells me so...
+# error: linking with `clang` failed: exit status: 1
+#   |
+#   = note: ld.lld: error: relocation R_MIPS_64 cannot be used against symbol 'DW.ref.rust_eh_personality'; recompile with -fPIC
+#           >>> defined in /usr/lib64/rustlib/mips64el-unknown-linux-gnuabi64/lib/libstd-6dcaeb4e3195ef4c.rlib(std-6dcaeb4e3195ef4c.std.fc0db18c60d19c82-cgu.0.rcgu.o)
+#           >>> referenced by std.fc0db18c60d19c82-cgu.0
+#           >>>               std-6dcaeb4e3195ef4c.std.fc0db18c60d19c82-cgu.0.rcgu.o:(.eh_frame+0x37B3) in archive /usr/lib64/rustlib/mips64el-unknown-linux-gnuabi64/lib/libstd-6dcaeb4e3195ef4c.rlib
+abinfo "Tweaking CFLAGS and CXXFLAGS..."
+if ab_match_arch loongson3 || \
+   ab_match_arch mips64r6el; then
+    export CFLAGS="${CFLAGS} -fPIC"
+    export CXXFLAGS="${CXXFLAGS} -fPIC"
+fi