CI: github: abandon asan matrix.py helper

that helper was useful in days when we beleived that gcc and clang
require different flags. those days are gone.

.github/matrix.py

@@ -86,14 +86,6 @@ def clean_compression(compression):
     return compression.replace("USE_", "").lower()
 
 
-def get_asan_flags(cc):
-    return [
-        "USE_OBSOLETE_LINKER=1",
-        'DEBUG_CFLAGS="-g -fsanitize=address"',
-        'LDFLAGS="-fsanitize=address"',
-        'CPU_CFLAGS.generic="-O1"',
-    ]
-
 def main(ref_name):
     print("Generating matrix for branch '{}'.".format(ref_name))
 
@@ -155,8 +147,11 @@ def main(ref_name):
                 "os": os,
                 "TARGET": TARGET,
                 "CC": CC,
-                "FLAGS": get_asan_flags(CC)
-                + [
+                "FLAGS": [
+                    "USE_OBSOLETE_LINKER=1",
+                    'DEBUG_CFLAGS="-g -fsanitize=address"',
+                    'LDFLAGS="-fsanitize=address"',
+                    'CPU_CFLAGS.generic="-O1"', 
                     "USE_ZLIB=1",
                     "USE_OT=1",
                     "OT_INC=${HOME}/opt-ot/include",