Remove symlink to seL4 kernel for sel4-sys build

- delete the symlink called "seL4"
- remove the manually specified SEL4_DIR environment variable from
Cargo.toml and move to .cargo/config.toml

bug: 202428321

Change-Id: I4f54b730e627a8445560e0e5e7bc056ab7e19062
GitOrigin-RevId: 17743c7034a37ac2dc0d036f405096213888f584

apps/system/components/.cargo/config.toml

@@ -0,0 +1,4 @@
+[env]
+# Pathname to seL4 kernel for xml files and (eventually) tools scripts,
+# defaults to "sel4" if not set
+SEL4_DIR = { value = "../../../../../kernel", relative = true }

apps/system/components/kata-os-common/src/sel4-sys/Cargo.toml

@@ -17,9 +17,6 @@ build = "build.rs"
 
 # NB: used by build.rs
 [env]
-# Pathname to seL4 kernel for xml files and (eventually) tools scripts,
-# defaults to "sel4"
-SEL4_DIR = "sel4"
 # Name of python3 interpreter executable, defaults to "python3"
 PYTHON = "python3"
 

apps/system/components/kata-os-common/src/sel4-sys/seL4

@@ -1 +0,0 @@
-../../../../../../../../kernel