Revert "Bump our Windows target to Windows 10."

This reverts commit 15b91ba4a67f3d12179d74c24f761d238c377fba.

Reason for revert: Studio wants more time.

Change-Id: I8e6080fd93de601de2a68881faebf847697f6927
diff --git a/cc/config/x86_windows_host.go b/cc/config/x86_windows_host.go
index 0450550..a4d43b9 100644
--- a/cc/config/x86_windows_host.go
+++ b/cc/config/x86_windows_host.go
@@ -33,10 +33,9 @@
 
 		// Use C99-compliant printf functions (%zd).
 		"-D__USE_MINGW_ANSI_STDIO=1",
-		// Target >= Windows 10.
-		// Both #defines are needed: https://learn.microsoft.com/en-us/cpp/porting/modifying-winver-and-win32-winnt?view=msvc-170
-		"-D_WIN32_WINNT=0x0A00",
-		"-DWINVER=0x0A00",
+		// Admit to using >= Windows 7. Both are needed because of <_mingw.h>.
+		"-D_WIN32_WINNT=0x0601",
+		"-DWINVER=0x0601",
 		// Get 64-bit off_t and related functions.
 		"-D_FILE_OFFSET_BITS=64",