Won't build on Linuxmint 21

[lbm-services]

2/54058] CXX obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o
FAILED: obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o 
clang++-14 -MMD -MF obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o.d -DUSE_UDEV -DUSE_AURA=1 -DUSE_GLIB=1 -DUSE_OZONE=1 -DOFFICIAL_BUILD -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_FORTIFY_SOURCE=2 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DNO_UNWIND_TABLES -D_GNU_SOURCE -DCR_CLANG_REVISION=\"llvmorg-17-init-4759-g547e3456-1\" -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -I../.. -Igen -Wall -Wextra -Wimplicit-fallthrough -Wextra-semi -Wunreachable-code-aggressive -Wthread-safety -Wno-missing-field-initializers -Wno-unused-parameter -Wno-psabi -Wloop-analysis -Wno-unneeded-internal-declaration -Wenum-compare-conditional -Wno-ignored-pragma-optimize -Wno-deprecated-builtins -Wno-bitfield-constant-conversion -Wno-deprecated-this-capture -Wshadow -fno-delete-null-pointer-checks -fno-ident -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -fno-unwind-tables -fno-asynchronous-unwind-tables -fPIC -pthread -fcolor-diagnostics -fmerge-all-constants -fcrash-diagnostics-dir=../../tools/clang/crashreports -mllvm -instcombine-lower-dbg-declare=0 -ffp-contract=off -m64 -msse3 -ffile-compilation-dir=. -no-canonical-prefixes -ftrivial-auto-var-init=pattern -O2 -fdata-sections -ffunction-sections -fno-unique-section-names -fno-omit-frame-pointer -gdwarf-4 -g1 -gdwarf-aranges -fvisibility=hidden -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wno-unused-const-variable -Wno-unused-function -std=c++20 -Wno-trigraphs -gsimple-template-names -fno-exceptions -fno-rtti -fvisibility-inlines-hidden -Wdate-time -D_FORTIFY_SOURCE=2 -O2 -ffile-prefix-map=/home/hli/Dokumente/_development/ungoogled-chromium-debian=. -fstack-protector-strong -Wformat -Werror=format-security -Wno-unknown-warning-option -Wno-deprecated-declarations -c ../../base/third_party/double_conversion/double-conversion/bignum-dtoa.cc -o obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o
../../base/third_party/double_conversion/double-conversion/bignum-dtoa.cc:28:10: fatal error: 'cmath' file not found
#include <cmath>
         ^~~~~~~
1 error generated.
[9/54058] CC obj/base/third_party/xdg_mime/xdg_mime/xdgmimecache.o
ninja: build stopped: subcommand failed.
make[1]: *** [debian/rules:143: override_dh_auto_build] Fehler 1
make[1]: Verzeichnis „/home/hli/Dokumente/_development/ungoogled-chromium-debian“ wird verlassen
make: *** [debian/rules:109: binary] Fehler 2
dpkg-buildpackage: Fehler: Unterprozess fakeroot debian/rules binary lieferte Exitstatus 2

[SugaryHull]

Is there a libstdc++-14-dev package available and, if so, is it installed? I tried to confirm myself, but Linux Mint's website doesn't have a way to search package versions that I could find.

[lbm-services]

seems not available, there is libstdc++-12-dev though.

[SugaryHull]

seems not available, there is libstdc++-12-dev though.

I misspoke before. That should be the one you need.