arm/classes: add support to configure fvp-bindir

Currently, fvp-bindir is configured to use the build path. This commit
allows customization of this path by defining a new variable FVP_BINDIR
in fvpconf. This change enables the runfvp script to execute without
BitBake initialization.

Testing:
- Tested using OpenBMC FVP build.
- Defined FVP_BINDIR variable with a custom path in fvp-config.inc and
observed the changes after the build.

Before changes:
$ jq . ~/openbmc/build/fvp/tmp/deploy/images/fvp/obmc-phosphor-image-fvp.fvpconf | grep
fvp-bindir
  "fvp-bindir": "/home/javith/build/openbmc/build/fvp/tmp/sysroots
-components/x86_64/fvp-base-a-aem-native/usr/bin",

After changes:
$ jq . ~/openbmc/build/fvp/tmp/deploy/images/fvp/obmc-phosphor-image-fvp.fvpconf | grep
fvp-bindir
  "fvp-bindir": "utilities/fvp/usr/bin",

Signed-off-by: Mohammed Javith Akthar M <mohammedjavitham@ami.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/classes/fvpboot.bbclass

@@ -48,7 +48,11 @@ python do_write_fvpboot_conf() {
     provider = d.getVar("FVP_PROVIDER")
     if provider:
         data["provider"] = provider
-        data["fvp-bindir"] = os.path.join(d.getVar("COMPONENTS_DIR"),
+        bindir = d.getVar("FVP_BINDIR")
+        if bindir:
+            data["fvp-bindir"] = bindir
+        else:
+            data["fvp-bindir"] = os.path.join(d.getVar("COMPONENTS_DIR"),
                                             d.getVar("BUILD_ARCH"),
                                             provider,
                                             "usr", "bin")