Add core/hyperthread count for Windows and Linux (#5216)

Add core/hyperthread count to `core:sys/info` for Windows and Linux.
TODO: Linux RISCV, Linux ARM, Darwin, and the BSDs.

core/sys/info/cpu_linux_intel.odin

@@ -0,0 +1,38 @@
+#+build i386, amd64
+#+build linux
+package sysinfo
+
+import "core:sys/linux"
+import "core:strings"
+import "core:strconv"
+
+@(init, private)
+init_cpu_core_count :: proc() {
+	fd, err := linux.open("/proc/cpuinfo", {})
+	if err != .NONE { return }
+	defer linux.close(fd)
+
+	// This is probably enough right?
+	buf: [4096]byte
+	n, rerr := linux.read(fd, buf[:])
+	if rerr != .NONE || n == 0 { return }
+
+	str := string(buf[:n])
+	for line in strings.split_lines_iterator(&str) {
+		key, _, value := strings.partition(line, ":")
+		key   = strings.trim_space(key)
+		value = strings.trim_space(value)
+
+		if key == "cpu cores" {
+			if num_physical_cores, ok := strconv.parse_int(value); ok {
+				cpu.physical_cores = num_physical_cores
+			}
+		}
+
+		if key == "siblings" {
+			if num_logical_cores, ok := strconv.parse_int(value); ok {
+				cpu.logical_cores = num_logical_cores
+			}
+		}
+	}
+}