Some parts of the build will use e.g. -O2 -mtune=generic otherwise.
--- a/solenv/gbuild/platform/ANDROID_AARCH64_GCC.mk
+++ b/solenv/gbuild/platform/ANDROID_AARCH64_GCC.mk
@@ -9,7 +9,7 @@
 
 # please make generic modifications to unxgcc.mk or android.mk
 gb_CPUDEFS += -DARM32
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/unxgcc.mk
 include $(GBUILDDIR)/platform/android.mk
--- a/solenv/gbuild/platform/ANDROID_ARM_GCC.mk
+++ b/solenv/gbuild/platform/ANDROID_ARM_GCC.mk
@@ -9,7 +9,7 @@
 
 # please make generic modifications to unxgcc.mk or android.mk
 gb_CPUDEFS += -DARM32
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/unxgcc.mk
 include $(GBUILDDIR)/platform/android.mk
--- a/solenv/gbuild/platform/ANDROID_INTEL_GCC.mk
+++ b/solenv/gbuild/platform/ANDROID_INTEL_GCC.mk
@@ -9,7 +9,7 @@
 
 # please make generic modifications to unxgcc.mk or android.mk
 gb_CPUDEFS += -DX86
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/unxgcc.mk
 include $(GBUILDDIR)/platform/android.mk
--- a/solenv/gbuild/platform/EMSCRIPTEN_INTEL_GCC.mk
+++ b/solenv/gbuild/platform/EMSCRIPTEN_INTEL_GCC.mk
@@ -73,7 +73,7 @@ ifeq ($(HAVE_EXTERNAL_DWARF),TRUE)
 gb_DEBUGINFO_FLAGS += -gsplit-dwarf -gpubnames
 endif
 
-gb_COMPILEROPTFLAGS := -O3
+gb_COMPILEROPTFLAGS :=
 
 # We need at least code elimination, otherwise linking OOMs even with 64GB.
 # So we "fake" -Og support to mean -O1 for Emscripten and always enable it for debug in configure.
--- a/solenv/gbuild/platform/LINUX_ARM_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_ARM_GCC.mk
@@ -9,7 +9,7 @@
 
 #please make generic modifications to unxgcc.mk or linux.mk
 gb_CPUDEFS += -DARM32
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_AXP_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_AXP_GCC.mk
@@ -8,7 +8,7 @@
 #
 
 #please make generic modifications to unxgcc.mk or linux.mk
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 gb_LinkTarget_LDFLAGS += -Wl,--no-relax
 
 include $(GBUILDDIR)/platform/linux.mk
--- a/solenv/gbuild/platform/LINUX_INTEL_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_INTEL_GCC.mk
@@ -9,7 +9,7 @@
 
 #please make generic modifications to unxgcc.mk or linux.mk
 gb_CPUDEFS := -DX86
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_M68K_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_M68K_GCC.mk
@@ -8,7 +8,7 @@
 #
 
 #please make generic modifications to unxgcc.mk or linux.mk
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_MIPS64_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_MIPS64_GCC.mk
@@ -9,7 +9,7 @@
 
 #please make generic modifications to unxgcc.mk or linux.mk
 gb_CPUDEFS += -DMIPS64
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_MIPS_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_MIPS_GCC.mk
@@ -9,7 +9,7 @@
 
 #please make generic modifications to unxgcc.mk or linux.mk
 gb_CPUDEFS += -DMIPS
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_POWERPC64_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_POWERPC64_GCC.mk
@@ -10,8 +10,7 @@
 #please make generic modifications to unxgcc.mk or linux.mk
 gb_CPUDEFS += -DPPC
 
-gb_COMPILEROPTFLAGS := -O2 \
-		       $(if $(filter powerpc64le-unknown-linux-gnu,$(HOST_PLATFORM)),-mtune=powerpc64le)
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_RISCV64_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_RISCV64_GCC.mk
@@ -8,7 +8,7 @@
 #
 
 #please make generic modifications to unxgcc.mk or linux.mk
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_SPARC64_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_SPARC64_GCC.mk
@@ -8,7 +8,7 @@
 #
 
 #please make generic modifications to unxgcc.mk or linux.mk
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_SPARC_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_SPARC_GCC.mk
@@ -8,7 +8,7 @@
 #
 
 #please make generic modifications to unxgcc.mk or linux.mk
-gb_COMPILEROPTFLAGS := -Os
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/LINUX_X86_64_GCC.mk
+++ b/solenv/gbuild/platform/LINUX_X86_64_GCC.mk
@@ -9,7 +9,7 @@
 
 #please make generic modifications to unxgcc.mk or linux.mk
 
-gb_COMPILEROPTFLAGS := -O2 -mtune=generic
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/linux.mk
 
--- a/solenv/gbuild/platform/NETBSD_INTEL_GCC.mk
+++ b/solenv/gbuild/platform/NETBSD_INTEL_GCC.mk
@@ -10,7 +10,7 @@
 #please make generic modifications to unxgcc.mk
 
 gb_CPUDEFS := -DX86
-gb_COMPILEROPTFLAGS := -O -g
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/unxgcc.mk
 
--- a/solenv/gbuild/platform/NETBSD_X86_64_GCC.mk
+++ b/solenv/gbuild/platform/NETBSD_X86_64_GCC.mk
@@ -9,7 +9,7 @@
 
 #please make generic modifications to unxgcc.mk
 
-gb_COMPILEROPTFLAGS := -O -g
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/unxgcc.mk
 
--- a/solenv/gbuild/platform/com_GCC_defs.mk
+++ b/solenv/gbuild/platform/com_GCC_defs.mk
@@ -38,7 +38,7 @@ endif
 gb_COMPILER_SETUP :=
 
 ifeq ($(strip $(gb_COMPILEROPTFLAGS)),)
-gb_COMPILEROPTFLAGS := -O2
+gb_COMPILEROPTFLAGS :=
 endif
 
 gb_COMPILEROPTFLAGS += $(if $(ENABLE_HARDENING_FLAGS),$(HARDENING_OPT_CFLAGS))
--- a/solenv/gbuild/platform/iOS.mk
+++ b/solenv/gbuild/platform/iOS.mk
@@ -24,7 +24,7 @@ ifeq ($(CXX),)
 $(error You must set CXX in the environment. See README.cross for example.)
 endif
 
-gb_COMPILEROPTFLAGS := -O2
+gb_COMPILEROPTFLAGS :=
 
 include $(GBUILDDIR)/platform/com_GCC_defs.mk