Just disable -Wundef for macos runners instead

The previous change to set TARGET_OS_EMBEDDED=0 didn't work
for libtommath which doesn't include Dropbear headers

.github/workflows/build.yml

@@ -53,8 +53,9 @@ jobs:
           - name: macos 10.15
             os: macos-10.15
             cc: clang
-            # OS X says daemon() and utmp are deprecated
-            extracflags: -Wno-deprecated-declarations
+            # OS X says daemon() and utmp are deprecated.
+            # OS X tests for undefined TARGET_OS_EMBEDDED in libc headers
+            extracflags: -Wno-deprecated-declarations -Wno-undef
             runcheck: 'no'
             apt: 'no'
             # fails with:
@@ -64,7 +65,7 @@ jobs:
           - name: macos 11
             os: macos-11
             cc: clang
-            extracflags: -Wno-deprecated-declarations
+            extracflags: -Wno-deprecated-declarations -Wno-undef
             runcheck: 'no'
             apt: 'no'
             ranlib: ranlib -no_warning_for_no_symbols

sysoptions.h

@@ -373,14 +373,4 @@
 #define DROPBEAR_MULTI 0
 #endif
 
-/* MacOSX10.15.sdk headers don't work with -Wundef */
-#ifdef __APPLE__
-
-#ifndef TARGET_OS_EMBEDDED
-#define TARGET_OS_EMBEDDED 0
-#endif
-
-#endif /* __APPLE__ */
-
-
 /* no include guard for this file */