armv7 targeting context: www/qt5-webengine poudriere build used "/usr/bin/c++ -B/usr/local/bin . . ." and failed : 'cmath' file not found

[This is a separate problem from another I sent to the
list earlier.]

My attempted bulk -a -c targeting armv7 (on a aarch64 machine
that can execute armv7 code) failed.

Note, from the log file:

[CA72_UFS] |   |   `-- Installing llvm13-13.0.1_2...
[CA72_UFS] |   |   | `-- Installing libedit-3.1.20210910,1...
[CA72_UFS] |   |   | `-- Extracting libedit-3.1.20210910,1: .......... done
[CA72_UFS] |   |   | `-- Installing lua53-5.3.6...
[CA72_UFS] |   |   | `-- Extracting lua53-5.3.6: .......... done
[CA72_UFS] |   |   | `-- Installing perl5-5.32.1_1...
[CA72_UFS] |   |   | `-- Extracting perl5-5.32.1_1: .......... done
[CA72_UFS] |   |   `-- Extracting llvm13-13.0.1_2: .......... done

So I'd expect llvm13's clang/clang++ and such to be in use.

But it ends up using /usr/bin/c++ as a path to a c++ but also using
-B/usr/local/bin in the same command. The combination ends up not
finding things like <cmath> --and that in turn leads to build
failure. (I show the first example but others happen before the
build  fully stops.)

From the logfile:

[  0% 12/21219] CXX obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o
FAILED: obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o 
/usr/bin/c++ -B/usr/local/bin -MMD -MF obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o.d -DUSE_AURA=1 -DUSE_NSS_CERTS=1 -DUSE_OZONE=1 -DOFFICIAL_BUILD -DTOOLKIT_QT -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DNO_UNWIND_TABLES -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -Igen -I../../../../qtwebengine-everywhere-src-5.15.2/src/3rdparty/chromium -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -Wno-unknown-attributes -Wno-unknown-pragmas -Wno-unknown-warning-option -fno-unwind-tables -fno-asynchronous-unwind-tables -fPIC -pthread -fcolor-diagnostics -fmerge-all-constants --target=arm-linux-gnueabihf -march=armv7-a -mfloat-abi=hard -mtune=generic-armv7-a -no-canonical-prefixes -mfpu=vfpv3-d16 -marm -Wall -Wextra -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -Wimplicit-fallthrough -Wunreachable-code -Wthread-safety -Wextra-semi -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -O2 -fno-ident -fdata-sections -ffunction-sections -fno-omit-frame-pointer -g0 -fvisibility=hidden -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wno-unused-const-variable -Wno-unused-function -Wno-parentheses-equality -Wno-tautological-compare -Wno-undefined-bool-conversion -Wno-tautological-undefined-compare -std=c++14 -fno-exceptions -fno-rtti -fvisibility-inlines-hidden -c ../../../../qtwebengine-everywhere-src-5.15.2/src/3rdparty/chromium/base/third_party/double_conversion/double-conversion/bignum-dtoa.cc -o obj/base/third_party/double_conversion/double_conversion/bignum-dtoa.o
../../../../qtwebengine-everywhere-src-5.15.2/src/3rdparty/chromium/base/third_party/double_conversion/double-conversion/bignum-dtoa.cc:28:10: fatal error: 'cmath' file not found
#include <cmath>
         ^~~~~~~
1 error generated.



For reference:

# ~/fbsd-based-on-what-commit.sh -C /usr/ports/
branch: main
merge-base: 0a2f0da65b65bb9b3abf7a06815854f3cff063fa
merge-base: CommitDate: 2022-05-07 18:07:34 +0000
0a2f0da65b65 (HEAD -> main) devel/py-tabulate: update to version 0.8.9
n582877 (--first-parent --count for merge-base)

# poudriere jail -jmain-CA7-bulk_a -i
Jail name:         main-CA7-bulk_a
Jail version:      14.0-CURRENT
Jail arch:         arm.armv7
Jail method:       null
Jail mount:        /usr/obj/DESTDIRs/main-CA7-poud-bulk_a
Jail fs:           
Jail updated:      2022-05-23 02:21:24
Jail pkgbase:      disabled

# uname -apKU # output line split for readability
FreeBSD CA72_UFS 14.0-CURRENT FreeBSD 14.0-CURRENT #56
main-n255745-77649f35a7e5-dirty: Sat May 21 18:48:32 PDT 2022
root@CA72_16Gp_ZFS:/usr/obj/BUILDs/main-CA72-nodbg-clang/usr/main-src/arm64.aarch64/sys/GENERIC-NODBG-CA72
arm64 aarch64 1400059 1400059

The jail is based on a armv7 build of the same source tree as
used for the above.

===
Mark Millard
marklmi at yahoo.com