depends: hard-code necessary c(xx)flags rather than setting them per-host

The per-host flag variables hold platform-specific defaults that are ignored
when flag environment variables are set, so it was wrong for them to contain
-std options relied on by package definitions.

Additionally, these flags (-pipe and -std=xx) will no longer be passed into
the CMake build, meaning less duplication in the build summary.

Pulled out of #31920.

depends/funcs.mk

@@ -8,9 +8,11 @@ $(1)_ar=$$($$($(1)_type)_AR)
 $(1)_ranlib=$$($$($(1)_type)_RANLIB)
 $(1)_nm=$$($$($(1)_type)_NM)
 $(1)_cflags=$$($$($(1)_type)_CFLAGS) \
-            $$($$($(1)_type)_$$(release_type)_CFLAGS)
+            $$($$($(1)_type)_$$(release_type)_CFLAGS) \
+            -pipe -std=$(C_STANDARD)
 $(1)_cxxflags=$$($$($(1)_type)_CXXFLAGS) \
-              $$($$($(1)_type)_$$(release_type)_CXXFLAGS)
+              $$($$($(1)_type)_$$(release_type)_CXXFLAGS) \
+              -pipe -std=$(CXX_STANDARD)
 $(1)_ldflags=$$($$($(1)_type)_LDFLAGS) \
              $$($$($(1)_type)_$$(release_type)_LDFLAGS) \
              -L$$($($(1)_type)_prefix)/lib