Restore gccmaths on vx7r2cert except on x86_64

When we started testing against helix-cert (on x86_64), we saw that
its cert GOS was providing gccmaths routines; so we figured that we
would not want to provide ours, otherwise we would have a conflict at
link time.  This was implemented by eng/toolchain/bb-runtimes!94.
However, this turned out to be a peculiarity of the x86_64 platform
(and possibly a bug there); aarch64 helix-cert GOS does not provide
gccmaths (neither the other architecture over vx7r2 safety profile
like ppc*, for what it's worth).  All in all, the proper solution at
this point is to provide gccmaths on all vx7r2cert platforms except
x86_64.

eng/toolchain/acats#21

support/rts_sources/sources.py

@@ -446,6 +446,42 @@
         "conditions": ["Add_Command_Line:yes"],
         "srcs": ["libgnat/a-comlin.ads", "libgnat/a-comlin.adb", "argv.c", "runtime.h"],
     },
+    "gccmath": {
+        # gcc maths intrinsics are provided on no supported configuration
+        # of vx7r2cert (neither safety profile nor helix-cert)
+        # *except* x86_64 helix-cert.
+        "conditions": [
+            "CPU_Family:arm,aarch64,ppc,ppc64,x86",
+            "RTS_Profile:light,light-tasking",
+            "Target_Word_Size:64",
+        ],
+        "srcs": [],
+        "vx7r2cert_srcs": [
+            "hie/s-gcc.ads",
+            "hie/s-gcc-ti.ads",
+            "hie/s-gcc-ti.adb",
+            "hie/s-gtasl3.ads",
+            "hie/s-gtasl3.adb",
+            "hie/s-gtasr3.ads",
+            "hie/s-gtasr3.adb",
+            "hie/s-gtlsr3.ads",
+            "hie/s-gtlsr3.adb",
+            "hie/s-gtimo3.ads",
+            "hie/s-gtimo3.adb",
+            "hie/s-gtium3.ads",
+            "hie/s-gtium3.adb",
+            "hie/s-gcdimo.ads",
+            "hie/s-gcdimo.adb",
+            "hie/s-gudmo4.ads",
+            "hie/s-gudmo4.adb",
+            "hie/s-gtdmo3.ads",
+            "hie/s-gtiud3.ads",
+            "hie/s-gtiud3.adb",
+            "hie/s-gtidi3.ads",
+            "hie/s-gtidi3.adb",
+            "hie/s-gtumo4.ads",
+        ],
+    },
     "full": {
         "conditions": ["RTS_Profile:embedded"],
         "srcs": [