Revert "src.opts.mk: Default LLVM_ASSERTIONS off"

Enabling and disabling LLVM assertions changes the ABI. There have
been multiple reports on the freebsd-current@ mailing list of broken
'cc'.

Out of caution, you may wish to do a clean build while crossing this
commit after building the reverted commit if you do not set
LLVM_ASSERTIONS in your src.conf.

Discussed with:	kevans, jrtc27

This reverts commit 9b3055d0d4.

UPDATING

@@ -42,11 +42,6 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 15.x IS SLOW:
 	package, FreeBSD-bmake.  If you use pkgbase and you need make, you
 	should install this package.
 
-20250727:
-	LLVM's debugging assertions are now disabled in main by default.
-	The WITH_LLVM_ASSERTIONS src.conf(5) knob should be used to
-	enable it when working on LLVM or requesting help with it.
-
 20250726:
 	amd64 kernel configurations must contain "options SMP".
 

share/man/man5/src.conf.5

@@ -1,5 +1,5 @@
 .\" DO NOT EDIT-- this file is @generated by tools/build/options/makeman.
-.Dd July 27, 2025
+.Dd July 14, 2025
 .Dt SRC.CONF 5
 .Os
 .Sh NAME
@@ -940,9 +940,8 @@ amd64/amd64, arm64/aarch64, i386/i386, powerpc/powerpc64 and powerpc/powerpc64le
 Do not build the LLD linker during the bootstrap phase of
 the build.
 To be able to build the system an alternate linker must be provided via XLD.
-.It Va WITH_LLVM_ASSERTIONS
-Enable debugging assertions in LLVM.
-Use when working on or requesting help with LLVM components.
+.It Va WITHOUT_LLVM_ASSERTIONS
+Disable debugging assertions in LLVM.
 .It Va WITHOUT_LLVM_BINUTILS
 Install ELF Tool Chain's binary utilities instead of LLVM's.
 This includes

share/mk/src.opts.mk

@@ -123,6 +123,7 @@ __DEFAULT_YES_OPTIONS = \
     LEGACY_CONSOLE \
     LLD \
     LLD_BOOTSTRAP \
+    LLVM_ASSERTIONS \
     LLVM_BINUTILS \
     LLVM_COV \
     LLVM_CXXFILT \
@@ -209,7 +210,6 @@ __DEFAULT_NO_OPTIONS = \
     HESIOD \
     LOADER_VERBOSE \
     LOADER_VERIEXEC_PASS_MANIFEST \
-    LLVM_ASSERTIONS \
     LLVM_FULL_DEBUGINFO \
     MALLOC_PRODUCTION \
     OFED_EXTRA \

tools/build/options/WITH_LLVM_ASSERTIONS

@@ -1,2 +1 @@
 Enable debugging assertions in LLVM.
-Use when working on or requesting help with LLVM components.