[factor out is_musl.mak]

Author: kinke

druntime/test/exceptions/Makefile

@@ -1,17 +1,9 @@
-ifndef IS_MUSL # LDC defines it externally
-    ifeq ($(OS),linux)
-        # FIXME: detect musl libc robustly; just checking Alpine Linux' apk tool for now
-        ifeq (1,$(shell which apk >/dev/null 2>&1 && echo 1))
-            IS_MUSL := 1
-        endif
-    endif
-endif
-
 TESTS=stderr_msg unittest_assert invalid_memory_operation static_dtor \
       future_message refcounted rt_trap_exceptions_drt catch_in_finally \
       message_with_null
 
 # FIXME: segfaults with musl libc
+include ../is_musl.mak
 ifneq ($(IS_MUSL),1)
 TESTS += unknown_gc
 endif

druntime/test/importc_compare/Makefile

@@ -1,16 +1,8 @@
 TESTS := importc_compare
 
-ifndef IS_MUSL # LDC defines it externally
-    ifeq ($(OS),linux)
-        # FIXME: detect musl libc robustly; just checking Alpine Linux' apk tool for now
-        ifeq (1,$(shell which apk >/dev/null 2>&1 && echo 1))
-            IS_MUSL := 1
-        endif
-    endif
-endif
-
 # FIXME: fails on Alpine v3.21 with conflicting struct declarations in the C headers:
 # /usr/include/asm-generic/fcntl.h(195): Error: struct `importc_includes.flock` conflicts with struct `importc_includes.flock` at /usr/include/fcntl.h(24)
+include ../is_musl.mak
 ifeq ($(IS_MUSL),1)
     TESTS :=
 endif