Use -isystem instead of -I for Sources; prevents Math.h shadowing <math.h>

On case-insensitive filesystems, -I$(top_srcdir)/Sources causes
<math.h> to resolve to ObjectivelyGPU/Math.h. -isystem places the
project include path after real system headers in the search order.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jdolan

Examples/Makefile.am

@@ -5,7 +5,7 @@ noinst_PROGRAMS = \
 	HelloCompute
 
 CFLAGS += \
-	-I$(top_srcdir)/Sources \
+	-isystem $(top_srcdir)/Sources \
 	@HOST_CFLAGS@ \
 	@OBJECTIVELY_CFLAGS@ \
 	@SDL3_CFLAGS@

Sources/ObjectivelyGPU/Makefile.am

@@ -1,5 +1,5 @@
 AUTOMAKE_OPTIONS = nostdinc
-AM_CPPFLAGS = -I$(top_srcdir)/Sources -iquote$(top_builddir)/Sources/ObjectivelyGPU
+AM_CPPFLAGS = -isystem $(top_srcdir)/Sources -iquote$(top_builddir)/Sources/ObjectivelyGPU
 
 noinst_HEADERS = \
     Config.h